criterion update: add "switch user" to Shutdown, reboot, logout

[Kevin Kofler]

I wrote:
> GNOME these days supports user switching ONLY with GDM. :-( (Yet another
> example of how GNOME does not give a darn about interoperability with
> anything else.) Even with GDM, it could be broken, but with other display
> managers, it is not even expected to work anymore.

PS: Oh, and while for user switching, this has been the case already for a 
while, recently, GNOME has started requiring GDM even for SCREEN LOCKING! 
(!!!)

        Kevin Kofler