* This backend permit mods to store extra players attributes to a common interface.
* Add the obj:set_attribute(attr, value) Lua call
* Add the obj:get_attribute(attr) Lua call
Examples:
* player:set_attribute("home:home", "10,25,-78")
* player:get_attribute("default:mana")
Attributes are saved as a json in the player file in extended_attributes
key
They are saved only if a modification on the attributes occurs and loaded
when emergePlayer is called (they are attached to PlayerSAO).
* 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
