b2e871bd48
This allows drivers to provide consistent flat shading for quads. Otherwise a driver that only supported tris would have to force last provoking vertex when drawing quads (and would have to say that quads don't follow the provoking vertex convention). Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu> Reviewed-by: Rob Clark <robclark@freedesktop.org>