xwl_glamor_eglstream_init_egl() uses "EGL_IMG_context_priority"
extension, make sure it's actually available before using it.
Suggested-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>