Add surface opacity controls.
Add surface opacity controls.

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