* LocalPlayer take ownership of maxHudId as it's the only caller
* RemotePlayer take ownership of day night ratio as it's the only user
* Pass getPlayerControl as const reference to prevent object copy on each call (perf improvement in ObjectRef::l_get_player_control call)
* getPlayerSAO is now only RemotePlayer call
* get/setHotbarItemCount is now RemotePlayer owned
* Server: Use RemotePlayer instead of Player object on concerned call to properly fix the object type
* PlayerSAO now uses RemotePlayer instead of Player because it's only server side
* ObjectRef::getplayer also returns RemotePlayer as it's linked with PlayerSAO

	The initial problem was that mutex_auto_lock.h tries to use std::unique_lock<std::mutex>
	despite mutex.h not using C++11's std::mutex on Windows. The problem here is the mismatch
	between C++11 usage conditions of the two headers. This commit moves the decision logic
	to threads.h and makes sure mutex.h, mutex_auto_lock.h and event.h all use the same features.

Also remove some unused parameters/functions

Fixes #4579, a regression introduced by commit

d4c76258 "Chat: new settings to prevent spam"

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