Blender Git Loki

Doversion: We should always add the old RenderLayer

We cannot assume a render layer does not have a setting that was needed for
compositing. Even if:

```
(scene->lay & render_layer->lay) != (scene_lay) &&
(render_layer->lay | render_layer->lay_exclude) == 0))
```

Which would mean use the scene layers just as they are.