Added the following chat coreside features
* Chat messages length limit
* Message rate limiting
* Message rate kicking

Note:
* handleChat now takes RemotePlayer pointer instead of u16 to remove useless
  lookups

Adds several new ways that the plantlike drawtype mesh can be changed.

This requires paramtype2 = "meshoptions" to be set in the node
definition. The drawtype for these nodes should be "plantlike".

These modifications are all done using param2. This field is now
a complex bitfield that allows some or more of the combinations to
be chosen, and the mesh draw code will choose the options based as
neeeded for each plantlike node.

bit layout:
bits 0, 1 and 2 (values 0x1 through 0x7) are for choosing the plant
mesh shape:
  0 - ordinary plantlike plant ("x" shaped)
  1 - ordinary plant, but rotated 45 degrees ("+" shaped)
  2 - a plant with 3 faces ("*" shaped)
  3 - a plant with 4 faces ("#" shaped)
  4 - a plant with 4 faces ("#" shaped, leaning outwards)
  5 through 7 are unused and reserved for future mesh shapes.

bit 3 (0x8) causes the plant to be randomly offset in the x,z
plane. The plant should fall within the 1x1x1 nodebox if regularly
sized.

bit 4 (0x10) causes the plant mesh to grow by sqrt(2), and will cause
the plant mesh to fill out 1x1x1, and appear slightly larger. Texture
makers will want to make their plant texture 23x16 pixels to have the
best visual fit in 1x1x1 size.

bit 5 (0x20) causes each face of the plant to have a slight negative
Y offset in position, descending up to 0.125 downwards into the node
below. Because this is per face, this causes the plant model to be
less symmetric.

bit 6 (0x40) through bit 7 (0x80) are unused and reserved for
future use.

!(https://youtu.be/qWuI664krsI)

Adds the particle option `collision_removal = bool`

Some particles are hard to use right now since they either go through
solid blocks (without collision detection), and with collision
detection enabled they (e.g. raindrops) would just stop dead on the
floor and sit there until they expire, or worse, scrape along a wall
or ceiling.

We can solve the problem by adding a boolean flag that tells the
particle to be removed if it ever collides with something. This will
make it easier to add rain that doesn't fall through your roof or stick
on the top of it. Or clouds and smoke that don't go through trees.

Particles that collide with this flag are marked expired
unconditionally, causing them to be treated like normal expired
particles and cleaned up normally.

Documentation is adjusted accordingly.

An added bonus of this patch is that particles can potentially collide
many times with nodes, and this reduces the amount of collisions to 1
(max), which may end up reducing particle load on the client.

Fixes a bug where packet reordering made the server give the
client two peer ids instead of one. This in turn confused
reliable packet sending and made connecting to the server fail.

The client usually sends three packets at init: one "dummy"
packet consisting of two 0 bytes, and the init packet as well as
its legacy counterpart. The last one can be turned off since commit
af301831, but this is of lower
relevance for the bug. The relevant part here is that network
packet reorder (which is a normal occurence) can make the packets
reach the server in different order.

If reorder puts the dummy packet further behind, the following
would happen before the patch:

1. The server will get one of the init packets on channel 1 and
   assign the client a peer id, as the packet will have zero as
   peer id.

2. The server sends a CONTROLTYPE_SET_PEER_ID packet to inform
   the client of the peer id.

3. The next packet from the client will contain the peer id set by
   the server.

4. The server sets the m_has_sent_with_id member for the client's
   peer structure to true.

5. Now the dummy packet arrives. It has a peer id of zero, therefore
   the server searches whether it already has a peer id for the
   address the packet was sent from. The search fails because
   m_has_sent_with_id was set to true and the server only searched
   for peers with m_has_sent_with_id set to false.

6. In a working setup, the server would assign the dummy packet to
   the correct peer id. However the server instead now assigns a
   second peer id and peer structure to the peer, and assign the
   packet to that new peer.

7. In order to inform the peer of its peer id, the server sends a
   CONTROLTYPE_SET_PEER_ID command packet, reliably, to the peer.
   This packet uses the new peer id.

8. The client sends an ack to that packet, not with the new peer id
   but with the peer id sent in 2.

9. This packet reaches the server, but it drops the ACK as the peer
   id does not map to any un-ACK-ed packets with that seqnum. The
   same time, the server still waits for an ACK with the new peer
   id, which of course won't come. This causes the server to
   periodically re-try sending that packet, and the client ACKing it
   each time.

Steps 7-9 cause annoyances and erroneous output, but don't cause
the connection failure itself.
The actual mistake that causes the connection failure happens in 6:
The server does not assign the dummy packet to the correct peer, but
to a newly created one.
Therefore, all further packets sent by the client on channel 0 are
now buffered by the server as it waits for the dummy packet to reach
the peer, which of course doesn't happen as the server assigned
that packet to the second peer it created for the client.
This makes the connection code indefinitely buffer the
TOSERVER_CLIENT_READY packet, not passing it to higher level code,
which stalls the continuation of the further init process
indefinitely and causes the actual bug.

Maybe this can be caused by reordered init packets as well, the only
studied case was where network has reliably reordered the dummy
packet to get sent after the init packets.

The patch fixes the bug by not ignoring peers where
m_has_sent_with_id has been set anymore. The other changes of the
patch are just cleanups of unused methods and fields and additional
explanatory comments.

One could think of alternate ways to fix the bug:

* The client could simply take the new peer id and continue
  communicating with that. This is however worse than the fix as
  it requires the peer id set command to be sent reliably (which
  currently happens, but it cant be changed anymore). Also, such a
  change would require both server and client to be patched in order
  for the bug to be fixed, as right now the client ignores peer id
  set commands after the peer id is different from
  PEER_ID_INEXISTENT and the server requires modification too to
  change the peer id internally.
  And, most importantly, right now we guarantee higher level server
  code that the peer id for a certain peer does not change. This
  guarantee would have to be broken, and it would require much
  larger changes to the server than this patch means.

* One could stop sending the dummy packet. One may be unsure whether
  this is a good idea, as the meaning of the dummy packet is not
  known (it might be there for something important), and as it is
  possible that the init packets may cause this problem as well
  (although it may be possible too that they can't cause this).

Thanks to @auouYmous who had originally reported this bug and who
has helped patiently in finding its cause.

Writing an u8 to verbosestream writes a char, not it's numeric value.

Changes:
  * Fix indentation.
  * Pass strings by const reference.
  * Merge Strfnd and WStrfnd into one class instead of copying them.
  * Remove trailing spaces.
  * Fix variable names.
  * Move to util.
  * Other miscellaneous style fixes.

The legacy init packet (pre v25) sends information about the client's
password that a server could use to log in to other servers if the
username and password are the same. All the other benefits of SRP of
protocol v25 are missed if the legacy init packet is still sent during
connection creation.

This patch adds an option to not send the v25 init packet. Not sending
the v25 packet means breaking compat with pre v25 servers, but as the
option is not enabled by default, no servers are affected unless the
user explicitly flips the switch. More than 90% of the servers on the
serverlist support post v25 protocols.

The patch also fixes a bug with greying out of non compliant servers
being done wrongly, the min and max params were mixed.

* No function overloading
* Adhere coding style and with method names following
  lowercase_underscore_style
* Use std::string in external API, handling these is
  much more fun

Only set back position when sneaking if player wasn't teleported by adding and using a bool "got_teleported" to player
it fixes #2876

We introduce a new nodebox type "connected", and allow these nodes to
have optional nodeboxes that connect it to other connecting nodeboxes.

This is all done at scenedraw time in the client. The client will
inspect the surrounding nodes and if they are to be connected to,
it will draw the appropriate connecting nodeboxes to make those
connections.

In the node_box definition, we have to specify separate nodeboxes for
each valid connection. This allows us to make nodes that connect only
horizontally (the common case) by providing optional nodeboxes for +x,
-x, +z, -z directions. Or this allows us to make wires that can connect
up and down, by providing nodeboxes that connect it up and down (+y,
-y) as well.

The optional nodeboxes can be arrays. They are named "connect_top,
"connect_bottom", "connect_front", "connect_left", "connect_back" and
"connect_right". Here, "front" means the south facing side of the node
that has facedir = 0.

Additionally, a "fixed" nodebox list present will always be drawn,
so one can make a central post, for instance. This "fixed" nodebox
can be omitted, or it can be an array of nodeboxes.

Collision boxes are also updated in exactly the same fashion, which
allows you to walk over the upper extremities of the individual
node boxes, or stand really close to them. You can also walk up
node noxes that are small in height, all as expected, and unlike the
NDT_FENCELIKE nodes.

I've posted a screenshot demonstrating the flexibility at
    http://i.imgur.com/zaJq8jo.png
In the screenshot, all connecting nodes are of this new subtype.

Transparent textures render incorrectly, Which I don't think is
related to this text, as other nodeboxes also have issues with this.

A protocol bump is performed in order to be able to send older clients
a nodeblock that is usable for them. In order to avoid abuse of users
we send older clients a "full-size" node, so that it's impossible for
them to try and walk through a fence or wall that's created in this
fashion. This was tested with a pre-bump client connected against a
server running the new protocol.

These nodes connect to other nodes, and you can select which ones
those are by specifying node names (or group names) in the
connects_to string array:
      connects_to = { "group:fence", "default:wood" }
By default, nodes do not connect to anything, allowing you to create
nodes that always have to be paired in order to connect. lua_api.txt
is updated to reflect the extension to the node_box API.

Example lua code needed to generate these nodes can be found here:
    https://gist.github.com/sofar/b381c8c192c8e53e6062

Outdated servers are always sending tiledefs with culling
enabled no matter what, as the value was previously entirely
ignored.

To compensate, we must (1) detect that we're running against
an old server with a new client, and (2) disable culling for
mesh, plantlike, firelike and liquid draw types no matter what
the server is telling us.

In order to achieve this, we need to bump the protocol version
since we cannot rely on the tiledef version, and test for it
being older. I've bumped the protocol version, although that
should have likely happened in the actual change that introduced
the new backface_culling PR #3578. Fortunately that's only 2
commits back at this point.

We also explicitly test for the drawtype to assure we are not
changing the culling value for other nodes, where it should
remain enabled.

This was tested against various pub servers, including 0.4.13 and
0.4.12.

Fixes #3598

Fix for commit 87dcee6a It uses the wrong variable and only covers some use cases. This change covers all use cases.

Fix regression of commit

5e507c98 "Add server side ncurses terminal"

which allowed all players, even those without a shout priv, to chat.

Fixes #3362.

This adds a chat console the server owner can use for administration
or to talk with players.
It runs in its own thread, which makes the user interface immune to
the server's lag, behaving just like a client, except timeout.
As it uses the same console code as the f10 console, things like nick
completion or a scroll buffer basically come for free.
The terminal itself is written in a general way so that adding a
client version later on is just about implementing an interface.

Fatal errors are printed after the console exists and the ncurses
terminal buffer gets cleaned up with endwin(), so that the error still
remains visible.

The server owner can chose their username their entered text will
have in chat and where players can send PMs to.
Once the username is secured with a password to prevent anybody to
take over the server, the owner can execute admin tasks over the
console.

This change includes a contribution by @kahrl who has improved ncurses
library detection.

Remove DTIME macro and its uses, too

- SRP: print the address only once, not twice
- Legacy: previously the address was not printed at all
- Make both messages structurally the same, to facilitate log analyzers

1. Do two renames:
	* SER_FMT_CLIENT_VER_LOWEST -> SER_FMT_VER_LOWEST_WRITE
	* SER_FMT_VER_LOWEST -> SER_FMT_VER_LOWEST_READ
Now the two define values are consistently named with the _WRITE defines
SER_FMT_VER_{HIGHEST,LOWEST}_WRITE, and to better point out what the two
serialisation versions actually are for.

2. wrap some lines in doc/worldformat.txt, and point out that the node
timers are serialized at a later point, as this can cause confusion about
what now happens (if one doesn't strictly read the if block's conditions).

3. some whitespace fixes in NodeTimerList::serialize, and one new comment.

Its obvious that "u16 command" is inside every packet, therefore this
commit removes all mentions of the command, if non-array like notation
is used. We already didn't add "u16 command" to new packets or removed
it at packet changes, so now we remove it from existing packets.

  * Rename everything.
    * Strip J prefix.
    * Change UpperCamelCase functions to lowerCamelCase.
  * Remove global (!) semaphore count mutex on OSX.
  * Remove semaphore count getter (unused, unsafe, depended on internal
    API functions on Windows, and used a hack on OSX).
  * Add `Atomic<type>`.
  * Make `Thread` handle thread names.
  * Add support for C++11 multi-threading.
  * Combine pthread and win32 sources.
  * Remove `ThreadStarted` (unused, unneeded).
  * Move some includes from the headers to the sources.
  * Move all of `Event` into its header (allows inlining with no new includes).
  * Make `Event` use `Semaphore` (except on Windows).
  * Move some porting functions into `Thread`.
  * Integrate logging with `Thread`.
  * Add threading test.

This was caused by the use the non-threadsafe SharedBuffer in a
threaded context.

Thanks @Zeno-

This was needed due to the TileDef serialisation changes. Originally it has been planned
to also add utf-8 based chat to 26, but chat changes aren't final yet, so they are done
in one change, after the release, and not two small ones, causing us having to be compliant
to three versions of the packet.

Enable the server to request the client to reconnect.

This can be done with the now extended minetest.request_shutdown([reason], [reconnect]) setting.

-> Fix server crash with protocol >=25 if a default password is set.
-> Remove some useless and possibly confusion causing code for the TOCLIENT_FIRST_SRP packet handler