compositor: split weston_surface_update_transform()

Split two helper functions out of weston_surface_update_transform() to:
- make the code clearer
- update the bounding box properly even if transformation fails
- unify the return point

Also add a comment on what matrix.d[12] is.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
1 file changed