Log Message:
Update to Dovecot 1.1.16.

Fixes a couple of bugs in v1.1.15's changes. Hopefully the last v1.1 release
before v1.2.0.

- v1.1.15 could have crashed if mailbox-closing command was pipelined after a
  mailbox-accessing command.
- v1.1.15's zlib plugin may have caused crashes when fetching INTERNALDATE.
- Maildir: If messages had been deleted externally from new/ directory and
  mailbox was opened with EXAMINE, Dovecot didn't immediately notice that the
  messages were deleted.
- If message body started with a space, some operations could have assert-
  crashed.