compositor: Use pixman_region32_intersect_rect() instead of temp region
compositor: Use pixman_region32_intersect_rect() instead of temp region

We avoid reusing 'opaque' and don't leak the region.

kwm81/weston,sir-murray/weston,krezovic/weston,kwm81/weston,mchalupa/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,xorgy/weston,xorgy/weston,udoprog/weston,udoprog/weston,jonnylamb/weston,Fantu/compositor-spice,Fantu/compositor-spice,Gnurou/weston,eyolfson/weston,eyolfson/weston,sir-murray/weston,Gnurou/weston,giucam/weston,jonnylamb/weston,mchalupa/weston,Tarnyko/weston-xdg_surface_present,krezovic/weston,giucam/weston