mesa: Implement _mesa_all_varyings_in_vbos.

Implement the equivalent of vbo_all_varyings_in_vbos for
vertex array objects.

v2: Update comment.

Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/mesa/main/arrayobj.h

@@ -81,6 +81,10 @@ extern void
 _mesa_update_vao_client_arrays(struct gl_context *ctx,
                                struct gl_vertex_array_object *vao);
 
+/* Returns true if all varying arrays reside in vbos */
+extern bool
+_mesa_all_varyings_in_vbos(const struct gl_vertex_array_object *vao);
+
 /*
  * API functions
  */