Properly and efficiently use split utility headers

src/CMakeLists.txt

src/camera.cpp

src/camera.h

src/chat.cpp

src/client.cpp

src/client.h

src/clientmap.cpp

src/clientserver.h

src/connection.cpp

src/connection.h

src/constants.h

src/content_cao.cpp

src/content_mapblock.cpp

src/content_mapnode.cpp

src/content_nodemeta.cpp

src/content_sao.cpp

src/craftdef.cpp

src/environment.h

src/filecache.cpp

src/genericobject.cpp