Karmic: guest session is back

It has been broken for two months, since we upgraded to the “new” (not quite any more) gdm in Karmic: But I finally got around to re-doing the gdm patch for supporting a guest session for 2.27. I use it myself a lot for testing stuff with a clean user profile, so I can finally delete my herd of test users again.

One known drawback is that the guest session is not currently restricted by AppArmor rules yet. I’ll get to this at some point, I filed LP #425793 to keep it on the radar.