New ctx->Driver.Map/UnmapTexture() functions for accessing textures from t_vb_program.c

src/mesa/drivers/common/driverfuncs.c

@@ -112,6 +112,8 @@ _mesa_init_driver_functions(struct dd_function_table *driver)
    driver->DeleteTexture = _mesa_delete_texture_object;
    driver->NewTextureImage = _mesa_new_texture_image;
    driver->FreeTexImageData = _mesa_free_texture_image_data; 
+   driver->MapTexture = NULL;
+   driver->UnmapTexture = NULL;
    driver->TextureMemCpy = _mesa_memcpy; 
    driver->IsTextureResident = NULL;
    driver->PrioritizeTexture = NULL;