Make gtk_tree_model_foreach robust
Make gtk_tree_model_foreach robust

Make gtk_tree_model_foreach safe for callbacks that modify
the model, even if the model does not have persistent iters.

https://bugzilla.gnome.org/show_bug.cgi?id=722781

davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,ahodesuka/gtk,ahodesuka/gtk,jadahl/gtk,Adamovskiy/gtk,davidgumberg/gtk,jadahl/gtk,alexlarsson/gtk,ahodesuka/gtk,Lyude/gtk-,jigpu/gtk,chergert/gtk,jigpu/gtk,grubersjoe/adwaita,Adamovskiy/gtk,davidgumberg/gtk,alexlarsson/gtk,Adamovskiy/gtk,Lyude/gtk-,grubersjoe/adwaita,Adamovskiy/gtk,Lyude/gtk-,ahodesuka/gtk,ahodesuka/gtk,grubersjoe/adwaita,jigpu/gtk,alexlarsson/gtk,Adamovskiy/gtk,Adamovskiy/gtk,davidgumberg/gtk,jigpu/gtk,alexlarsson/gtk,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,grubersjoe/adwaita,Lyude/gtk-,alexlarsson/gtk,Adamovskiy/gtk,alexlarsson/gtk,davidgumberg/gtk,ahodesuka/gtk,alexlarsson/gtk,chergert/gtk,chergert/gtk,jadahl/gtk,chergert/gtk,jadahl/gtk,Lyude/gtk-,chergert/gtk,jigpu/gtk,chergert/gtk,davidgumberg/gtk,ahodesuka/gtk,jadahl/gtk,Lyude/gtk-,ahodesuka/gtk,Adamovskiy/gtk,jigpu/gtk,chergert/gtk,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidgumberg/gtk,Lyude/gtk-,jadahl/gtk,jadahl/gtk,Lyude/gtk-,grubersjoe/adwaita,jadahl/gtk