When the Language is changed in the Region panel, a "Restart"
notification is shown, but if the user closes the window without
acting on the restart session notification, there is no way to
get back to it.
This way we create a temporary file in the g_get_user_runtime_dir ()
directory flagging whether we should present the "Restart"
notification.
https://bugzilla.gnome.org/show_bug.cgi?id=702351