mesa: check glBegin()/glDrawArrays()/etc mode with _mesa_valid_prim_mode()

mesa: check glBegin()/glDrawArrays()/etc mode with _mesa_valid_prim_mode()

We now raise an GL_INVALID_ENUM in glBegin() if mode is illegal, as was
done in Yuanhan Liu's original patch.

Take geometry shaders support into account too.

Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>