Header file tweaking; mainly for speed

src/CMakeLists.txt

src/camera.cpp

src/camera.h

src/client.cpp

src/common_irrlicht.h

src/content_mapblock.cpp

src/content_mapnode.cpp

src/defaultsettings.cpp

src/defaultsettings.h

src/environment.cpp

src/game.cpp

src/guiInventoryMenu.cpp

src/guiKeyChangeMenu.cpp

src/guiMainMenu.cpp

src/guiMessageMenu.cpp

src/guiPasswordChange.cpp

src/guiPauseMenu.cpp

src/guiTextInputMenu.cpp

src/keycode.cpp

src/main.cpp