libbacklight: Add missing boilerplate to header
libbacklight: Add missing boilerplate to header

Use identical license and copyright as the .c file.

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