compositor-x11: Damage output when we receive expose events for the window
compositor-x11: Damage output when we receive expose events for the window

The gl renderer typically repaints everything since we don't have
EGL_buffer_age under X, but the pixman renderer carefully only repaints
damaged regions.  So to actually repaint anything with the pixman
renderer, we need to damage the output.

https://bugs.freedesktop.org/show_bug.cgi?id=72351

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