* Allow customization of the guest session with local scripts:
- Source /etc/guest-session/prepare.sh and /etc/guest-session/prefs.sh if
present.
- Allow the guest user read-write access to /var/guest-data/, to provide a
way to permanently store files. Note that the directory does not exist
by default, so to enable the feature you have to create it.
Thanks to Gunnar Hjalmarsson for the patches!