Update to Dovecot 1.1.13, there were two regressions in 1.1.12:

- v1.1.12's MAILBOXDIR changes broke accessing mails in some setups
- v1.1.12's login_executable -D checking changes caused dovecot to
  crash at startup if protocols setting contained only pop3.
- mbox: pop3_lock_session=3Dyes was broken with mail_privileged_group.

(ghen)