If exists, use Qt namespace.

Signed-off-by: Soroush Rabiei <soroush.rabiei@gmail.com>
Merge branch 'refs/heads/soroush-master' into Qt5

Conflicts:
	src/glc_context.cpp
	src/io/glc_3dstoworld.h
	src/io/glc_3dxmltoworld.h
	src/io/glc_fileloader.h
	src/shading/glc_light.h