Thunar: Don't display unmounted mount points in sidepane if built without mounting
My thunar is built without gvfs and without thunar-volman, so it can't mount volumes. However, it still displays all unmounted mount points (greyed) in the sidepane (both in tree and shortcut view). I think that's useless (because I can't mount them or use them in any way from within thunar), they should be suppressed if they can't be mounted..