adding support for hibernation to xfce4-sessions's exit dialog

[Jani Monoses]

> Yes, but more concrete: coorperate := Xfce + Xubuntu :-)

that goes without saying :)

> 
> Well, the "API" depends on the service interface, which is different for
> various applications (just compare Thunar and Terminal). You could add
> something like KUniqueApplication, but that doesn't make things easier
> in most cases, IMHO.

I think it's KUniqueApplication that was mentioned by some gnome devels
as a possibel source of inspiration but cannot find the thread or wikipage.

Jani