Cleanup Qt includes: include the directory name

Cleanup Qt includes: include the directory name
I use qmake for building QtAV so just including the filename in the QtAV *.cpp files is fine. But in the Application which I want to enhance with QtAV I'm not using qmake but a different make system. While I could also add the QtWidgets directory path to the include search path, I would really like to avoid doing this. And with this changes it should work for everyone.
Sorry that I was not more specific in the first place.
But you are right I overlooked the GraphicsItemRenderer.h. I will update this pull request.