GtkLabel: better treatment for selection with ellipsis
GtkLabel: better treatment for selection with ellipsis

This commit arranges things so that we treat an ellipsized
region like a single character for the purpose of selection
and cursor navigation.

https://bugzilla.gnome.org/show_bug.cgi?id=328449

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