Support unaligned QImage strides in QSGTexture

If a QImage has a different stride than its width, copy the image to
relayout the memory for compatibility with glTexImage2D().

Change-Id: I74338da97d785ffb9e00820caff36466dfa46838
Merge pull request #1 from mikkoharju/master

Pull in Support unaligned QImage strides in QSGTexture from upstream