nested: add missing egl extension declaration
nested: add missing egl extension declaration

Reviewed-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

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