Merged revisions 1832-1836 from stable (added dovecot support for debian squeeze and added a new distid and class for debian6 specific modifications.

the pwd is not longer stored in plaintext

fix bug FS#1200 - id elents should be unique. have changed side nav template, this needs to change too.

and
give nav list items unique ids (requires nav.css be changed too!)

The "new" php session-cleaning source works fine for several days at my servers, so we can delete the old (not working) one

BUG FS#1139 - fix as described in forum has been applied and tested by running script - no errors encountered. - and query checked with mysql.

as per bug #1177