This is part 2 for 5f084cd9

Other improvements:

* Use the defined ItemGroupList when used
* make Client::checkPrivilege const
* inline some trivial functions
* Add ActiveObjectMap typedef
* Add SettingsEntries typedef

* This permit to improve performance on C++11 builds
* use some existing typedefs in tools maps
* minor code style changes

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

Remove uses of std::map.
Make sure we use ContentFeatures reference not value.
Original commit by gregorycu.

'getSpawnLevelAtPoint()' did not account for disabled mountains, it
was possible to be spawned in mid-air where a mountain surface would
have been.

Avoid check for river area if rivers are disabled.

Fixes #4493.

This allows you to use an stdcall zlib (zlib1.dll instead of zlibwapi.dll)
when building Minetest for win32.

This commit fixes #4516, though note that this will gradually fix MapBlocks
as they are used/modified and thus re-serialized.

Add 'core.LIGHT_MAX = 14' to builtin/game/constants.lua with the intention
to replace misplaced 'default.LIGHT_MAX = 14' in Minetest Game.
Add comment in light.h requiring the constant be changed in both places.
Add lighting bug warning to note in lua_api.txt.
There are hundreds of mod uses of 15 which causes a lighting bug.

Inverts the given channels of the base image.
Mode may contain the characters "r", "g", "b", "a".
Only the channels that are mentioned in the mode string will be inverted.

In lua_api.txt, make clear that 'place on' and 'spawn by' can be lists.

Adds CMakeLists.txt include to fix this issue:

$ cmake . -DBUILD_SERVER=TRUE -DBUILD_CLIENT=FALSE \
   -DCMAKE_BUILD_TYPE=Release -DENABLE_CURL=TRUE -DENABLE_CURSES=FALSE \
   -DENABLE_FREETYPE=TRUE -DENABLE_GETTEXT=FALSE \
   -DENABLE_POSTGRESQL=FALSE -DENABLE_SOUND=FALSE -DENABLE_LUAJIT=TRUE \
   -DIRRLICHT_SOURCE_DIR=$HOME/irrlicht-1.8.4 -LH
...
CMake Error at src/CMakeLists.txt:339 (check_library_exists):
  Unknown CMake command "check_library_exists".
...

This snuck in with the meshoptions patch and accidentally kills
degrotate plants. Thanks to @hybriddog for finding this.

Fixes #4397

Rebased and tuned version of Calinou's original pull request.

'm_view_bobbing_speed' controls the frequency of view bobbing,
hand bobbing and footsteps, it was limited to a maximum of 40 (walking
frequency) so did not increase if player speed was modified by a
'speed buff', a sprinting mod or modified in .conf or advanced
settngs.

This commit raises the limit to 70 which is suitable for sprinting.

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)

Disable the ability to connect to old servers by default to
improve password security.

If people still want to connect to old (0.4.12 and earlier)
servers, they can flip the send_pre_v25_init setting.

Add the ability to detect if we've tried to connect
to a server which only supports the pre v25 init protocol,
and show an apropriate error message. Most times the error
will already be catched at the serverlist level, the
detection mechanism only acts as last resort, because the
"Connection timed out" error message that would be shown
otherwise would be very confusing.

Automatic "fixing" of this condition is not desired,
as it would allow for downgrade attacks.

As already 161 of the 167 servers on the serverlist
support the new srp based auth protocol (> 96%),
the breakage should be minimal.

Follow up of commit

af301831 "Add option to not send pre v25 init packet"

Also change the pessimistic assumption of masterlist
server versions to optimistic, in order to avoid buggy
behaviour (favourites not in the serverlist would be
denied to connect to, etc).

Fixes #4446: a syntax error that happens if something else (such as
<iomanip> or <locale> in certain libstdc++ versions) includes
<libintl.h> later, which contains a function declaration for gettext
that gets mangled by the macro.

See the added comment in gettext.h and the discussion in #4446/#4452
for details.

Fixes #4323.

* Multiline strings
* Table-concat instead of String-concats
* string.rep instead of loop-concat
* string.format %q instead of manual quotation by gsub
* Assert writeable files
* Generate new settings_translation_file