[Dovecot] 1.1.12 release candidate

http://dovecot.org/tmp/dovecot-1.1.12.rc.tar.gz

I would have already released 1.1.12, but it needed the MAILBOXDIR change described below, and I'm slightly worried that it might have broken some special setup. So please test first and I'll release in v1.1.12 then in a few days.

* Added :MAILBOXDIR= to mail_location to specify the root dir for
  mailboxes. dbox users should migrate to ":MAILBOXDIR=mailboxes",
  because that's going to be the default in v1.2+.

- IMAP: SELECT didn't always return first unseen message in reply
- POP3: pop3_lock_session=yes didn't use mail_privileged_group while
  dotlocking.
- mbox: Don't crash if >=8192 bytes long line begins with "From ".
- Maildir: More fixes to handling over 26 keywords.
- Several logging fixes and improvements
- Fixed authentication caching with non-plaintext mechanisms when
  using a blocking passdb (e.g. MySQL)
- Fixed DIGEST-MD5 authentication with user@domain style usernames.