use GLWidget and GL paint engine
Merge branch 'master' into gl
Merge branch 'master' into gl

Conflicts:
	src/libQtAV.pro
try to use gl commands. bug: crash, color is inverted, update not good
Merge branch 'gl' of github.com:wang-bin/QtAV into gl
Merge branch 'master' into gl
Merge branch 'master' into gl
gl: add GL_BGRA. correct the base class
gl: paintGL() must be in main thread(call update()). fix rotation and
flicker

it was in AVThread, so can't display the image
gl: aspect ratio change support

unlike other renderer, the paint on the whole widget surface. for
OpenGL, we glViewport explictly to set the area we can paint(out_rect)
gl: misc
Merge branch 'gl'