Ignore-this: b30b94c67baa8a8916dd216424e9473c

As auth_logoff is called very early for all not-logged in users it
prevented writing the breadcrumbs and might have broken some other
things relying on a open session at beginning of the script.

auth_logoff now makes sure the session is open but will not close
it.

Additionally the session is now explicitly closed before a redirect.

darcs-hash:20090210100257-7ad00-50470f18edb9fdbeb555fbf5d8a470a3b077915d.gz