[Bug 34151] Log out dialog need tooltips

[Lucas Nussbaum]

Public bug reported:
https://launchpad.net/malone/bugs/34151

Affects: gnome-session (Ubuntu)
       Severity: Normal
       Priority: (none set)
         Status: Unconfirmed

Description:
The "Log out" dialog desperately need some tooltips. It is difficult for
the user to know the difference between "sleep" and "hibernate" (which
one will still use some power, etc). Tooltips for other buttons would be
a good idea too.