Log Message:
Update to Dovecot 1.1.17.  manu's patch-ai has been included upstream.

- IMAP: Don't crash if IDLE command is pipelined after a long-running
  UID FETCH or UID SEARCH.
- IMAP: Some FETCH command parameters were broken with in some OSes.
- mbox: New mailboxes were created with UIDVALIDITY 1.
- mbox: Don't write garbage to mbox if message doesn't have a body.
- Maildir: Fixed using in-memory indexes when some required directory
  was missing.
- auth: Don't assert-crash if trying to log in as master user but
  with empty login username.
- Transaction log dotlocking ignored mail_nfs_index and
  dotlock_use_excl settings.
- convert plugin / convert-tool: Fixed changing hierarchy separators
  in mailbox names when alt_hierarchy_char isn't set.
- Several fixes to expire plugin / expire-tool
- zlib: Give better error messages on failures.