* squashed: CSM: Implement register_globalstep
* Re-use fatal error mechanism from server to disconnect client on CSM error
* Little client functions cleanups
* squashed: CSM: add core.after function
* core.after is shared code between client & server
* ModApiUtil get_us_time feature enabled for client
- Increase ContentFeatures serialization version
- Color property and palettes for nodes
- paramtype2 = "color", "colored facedir" or "colored wallmounted"
* Environment code refactoring
* Cleanup includes & class declarations in client & server environment to improve build speed
* ServerEnvironment::m_gamedef is now a pointer to Server instead of IGameDef, permitting to cleanup many casts.
* Cleanup IGameDef
* Move ITextureSource* IGameDef::getTextureSource() to Client only.
* Also move ITextureSource *IGameDef::tsrc() helper
* drop getShaderSource, getSceneManager, getSoundManager & getCamera abstract call
* drop unused emerge() call
* cleanup server unused functions (mentionned before)
* Drop one unused parameter from ContentFeatures::updateTextures
* move checkLocalPrivilege to Client
* Remove some unnecessary casts
* create_formspec_menu: remove IWritableTextureSource pointer, as client already knows it
* Fix some comments
* Change required IGameDef to Server/Client pointers
* Previous change that game.cpp sometimes calls functions with Client + InventoryManager + IGameDef in same functions but it's the same objects
* Remove duplicate Client pointer in GUIFormSpecMenu::GUIFormSpecMenu
* drop ClientMap::sectorWasDrawn which is unused
