Enable the server to request the client to reconnect.

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

- Fixed race conditions
- Fixed null dereference
- Fixed out-of-bounds array access
- MinimapMapblock is now allocated and added to update queue only when enabled
- Removed dependency on LocalPlayer
- Fixed code style
- Simplified expressions and program logic
- Cleaned minimap object interfaces

Previously, m_proto_ver was set to the serialisation version
inside the legacy init packet.

Now, if the server doesn't send a protocol version (protocols < 25),
we set m_proto_ver to some value < 25 and > 0.

Also, clean up surrounding code style
Replace by-value parameter passing with const refs when possible
Fix post-increment of iterators

This enables srp.

Adds everything needed for SRP (and everything works too),
but still deactivated, as protocol v25 init packets aren't final yet.
Can be activated by changing the LATEST_PROTOCOL_VERSION header to 25
inside networkprotocol.h.

Change types for passed password from wstring to string, which removes converting
back and forth in most cases. Move the narrow_to_wide conversion, where its neccessary,
closer to irrlicht. Remove trailing spaces in guiPasswordChange.cpp. Make parameters for
translatePassword passed as const reference.

NodeResolver name lists now belong to the NodeResolver object instead of
the associated NodeDefManager.  In addition to minimizing unnecessary
abstraction and overhead, this move permits NodeResolvers to look up nodes
that they had previously set pending for resolution.  So far, this
functionality has been used in the case of schematics for
serialization/deserialization.

Fixes #2603

Move debug streams to log.cpp|h

Move GUI-related globals to clientlauncher

Move g_settings and g_settings_path to settings.cpp|h

Move g_menuclouds to clouds.cpp|h

Move g_profiler to profiler.cpp|h

Because we get a Buffer<u8> from ConnectionEvent, don't convert it to SharedBuffer<u8> and return it to Server/Client::Receive which will convert it to NetworkPacket
Instead, put the Buffer<u8> directly to NetworkPacket and return it to packet processing
This remove a long existing memory copy
Also check the packet size directly into Connection::Receive instead of packet processing

Filename screenshot_ + ISO 8601 format + [-serial]

i.e. screenshot_YYYY-MM-DDTHH::MM::SS[-serial].png

Serial is added if the filename + timestamp already exists and is in the range 1 to 999

  * Combine client and server man pages.
  * Update unit test options and available databases in man page.
  * Add `--worldname` to man page.
  * Fix a bunch of places where `"Minetest"` was used directly instead of `PROJECT_NAME`.
  * Disable server build by default on all operating systems.
  * Make `ENABLE_FREETYPE` not fail if FreeType isn't found.
  * Enable LevelDB, Redis, and FreeType detection by default.
  * Remove the `VERSION_PATCH_ORIG` hack.
  * Add option to search for and use system JSONCPP.
  * Remove broken LuaJIT version detection.
  * Rename `DISABLE_LUAJIT` to `ENABLE_LUAJIT`.
  * Rename `minetest_*` variables in `version.{h,cpp}` to `g_*`.
  * Clean up style of CMake files.

* TOSERVER_INIT_LEGACY
* TOSERVER_DELETEDBLOCKS
* TOSERVER_GOTBLOCKS
* TOSERVER_REMOVED_SOUNDS
Also use a std::vector instead of std::set for TOSERVER_REMOVED_SOUNDS

The bar is only drawn when the user will notice a change, which prevents time overheads that this commit would cause, resulting from useless draws.

Rename some packet and handlers to <packet>_Legacy name for compat layer between new network changes and old network clients

Also change bzero to memset. bzero doesn't work on windows

For usages of assert() that are meant to persist in Release builds (when NDEBUG is defined), replace those usages with persistent alternatives

Performance improvement: Use std::list instead of std::vector for request_media, Server::getModNames, Environment::m_simple_objects.
* Also remove unused Server::m_modspaths

NetworkPacket.cpp:
* Remove some deprecated functions, we must use streaming interface
* m_data converted from u8* to std::vector<u8>
* Add an exporter to forge packet to Connection object
* implement operator << std::wstring. n
* implement operator << std::string
* dynamic resize when write packet content.
* fix string writing and performances.
* create ServerCommandFactory, used by client to get useful informations about packet processing (sending).
  * Reliability
  * Transmit channel
* Implement putRawString for some ugly char (_INIT packet), and use it.
* Many packet read and write migrated
* Implement oldForgePacket to interface writing with current connection
* fix U8/char/bool writing
* fix string writing and performances.
* add some missing functions
* Use v3s16 read instead of reading x,y,z separately
* Add irr::video::SColor support into packets
* Add some missing handlers
* Add a template function to increase offset
* Throw a serialization error on packet reading (must be improved)

PacketFactories:
* Create ServerCommandFactory, used by client to get useful informations about packet processing (sending).
* Create ClientCommandFactory, used by server to get useful informations about packet processing (sending).

Client.cpp:
* implement NetworkPacket ::Send interface.
* Move packet handlers to a dedicated file
* Remove Client::Send(SharedBuffer)

Server.cpp:
* implement NetworkPacket ::Send interface.
* Rewrite all packets using NetworkPacket
* Move packet handlers to a dedicated file
* Remove Server::Send(SharedBuffer)

ClientIface.cpp:
* Remove sendToAll(SharedBuffer<u8>)

Connection.hpp rework:
* Remove duplicate include
* Remove duplicate negation
* Remove a useless variable
* Improve code performance by using a m_peers_list instead of scanning m_peers map
* Remove Connection::Send(SharedBuffer)
* Fix useafterfree into NetworkPacket Sending
* Remove unused Connection::sendToAll

Test.cpp:
* Remove dead code
* Update tests to use NetworkPackets

Misc:
* add new wrappers to Send packets in client, using NetworkPacket
* Add NetworkPacket methods for Connection
* coding style fix
* dead code since changes cleanup
* Use v3s16 read instead of reading x,y,z separately in some packets
* Use different files to handle packets received by client and server
* Cleanup: Remove useless includes

ok @Zeno-
Tested by @Zeno- @VanessaE and @nerzhul on running servers

* Increase performance (client)
* Avoid changing a global value to solve a local problem

This reverts commit d25ff8fd.

* Increase performance (client)
* Avoid changing a global value to solve a local problem

* Move networkcode to a dedicated directory
* Rename clientserver.h to network/networkprotocol.h (Better name) and sanitize some includes
* Create object NetworkPacket
  * It stores command (opcode) and data separated
  * It also stores peer_id
  * Data reading can be done by using a streaming interface
* Change packet routing analysis
  * Remove old conditional analysis
  * Now uses function pointed analysis and add connection state ({Client,Server}::handlers)
  * Connection state permit to categorize condition to handle before analyze packets
  * Create a handler for depreciated messages, instead of duplicating code