Fix the pixman renderer with respect to output transforms
Commit
fa1b3055 introducted a regression in the pixman renderer. In
particular, it would not draw properly with any output transform other
than normal, 180, 180-flipped, or 270-flipped. This patch fixes this
regression. The weston-scalar program appears to work normally at all
rotations with this patch. Therefore, this patch should fix the regression
while maintaining the added functionality from
fa1b3055.
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>