Log Message:
libxfce4ui: Update to 4.13.0.

4.13.0
======
- Add xfce_widget_reparent to replace the deprecated gtk_widget_reparent
- Add xfce_titled_dialog_new_with_mixed_buttons to allow for setting
  icon names, button label text and response id.
- Add xfce_gtk_menu_popup_until_mapped as a convenience function to fix
  widespread problems with popping up menus (e.g. on keyboard shortcuts)
- Add dialog UI tests for Gtk2 and Gtk3
- Fix Glade Gtk3 support
- Fix a memory leak
- Translation updates: Asturian, Basque, Bulgarian, Catalan, Chinese
  (Taiwan), Croatian, Danish, English (Australia), Finnish, French, Galician,
  German, Greek, Hebrew, Hungarian, Icelandic, Korean, Lithuanian, Malay,
  Norwegian Bokmål, Occitan, Portuguese, Russian, Slovak, Slovenian, Spanish,
  Swedish