pixman-renderer: Add repaint debugging feature
pixman-renderer: Add repaint debugging feature

Add 'R' as a debug shortcut that highlights repainted regions.

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