scanner: Make fail() function use va_list and elaborate a few errors
scanner: Make fail() function use va_list and elaborate a few errors

bitfactor/wayland,eyolfson/wayland,mchalupa/wayland,bitfactor/wayland,mchalupa/wayland,eyolfson/wayland,sir-murray/wayland,tulcod/wayland,sir-murray/wayland,bitfactor/wayland,abooij/wayland,tulcod/wayland,abooij/wayland,mchalupa/wayland,abooij/wayland,eyolfson/wayland,sir-murray/wayland,tulcod/wayland