Support eglgralloctextures through QQuickWindow::createTexture().

Change-Id: I8cbdfde5b47beb849327e4ae61c5009005ffc79c
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Limit eglgralloctexture to 32-bit formats and make them all work.

Change-Id: I953d91550ceeb7f21dccfdc5515d3e19a6c16654
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
[qtscenegraph-adaptation] Fix non-32 bit and non-premultiplied images.

Merge branch 'codereview-master'

Conflicts:
	customcontext/texture/eglgralloctexture.cpp

Change-Id: Ia6513ea74e63a43ab14b16f522c7f29dfec8d49a