GtkDialog: Manage action area visibility more carefully
People expect to be able to call gtk_widget_show_all on the dialog to make action widgets visible, as seen e.g. in https://bugzilla.gnome.org/show_bug.cgi?id=733431 To keep this working, we can't always set no-show-all on the action_box. Only set it when the action_area is not used and empty.
Showing with 3 additions and 2 deletions