multimedia/xfce4-parole: Remove GST01 and CLUTTER options

• GStreamer 0.10 API has been removed since the 0.9.2 release.
• Clutter backend is blacklisted (it induces crash) with Gtk >= 3.22. Inform users that they need to switch to 'xvimagesink' or 'ximagesink'
• Add RUN_DEPENDS=devel/xdg-utils, as xdg-screensaver is used to inhibit the screensaver

Reported by: Olivier Duchateau <duchateau.olivier@gmail.com>