* subcompositor.c (DoCull): Fix leak of temp region upon
encountering opaque view.
* tests/subsurface_test.c (enum test_kind, test_names): New test
SUBSURFACE_GROW_SHRINK_KIND.
(LAST_TEST): Make it the last test.
(test_single_step): Implement SUBSURFACE_GROW_SHRINK_KIND.