Refactor: Improved DENG2_PRIVATE with std::auto_ptr

It is no longer necessary to always specify a destructor as auto_ptr
will delete the private instance automatically.
Merge branch 'master' of ssh://github.com/skyjake/Doomsday-Engine

Conflicts:
	doomsday/client/include/resource/textures.h
	doomsday/client/src/resource/texturemanifest.cpp
	doomsday/client/src/resource/textures.cpp
	doomsday/client/src/resource/texturescheme.cpp
Merge branch 'master' of ssh://github.com/skyjake/Doomsday-Engine
Cleanup