Log Message:
Update to dovecot-1.0rc18.  From the release announcement mail:

I think we're quite near v1.0 now.

	* ACL plugin + Maildir: Moved dovecot-acl file from control directory
	  to maildir. To prevent accidents caused by this change, Dovecot
	  kills itself if it finds dovecot-acl file from the control directory.
	* When opening a maildir, check if tmp/'s atime is over 8h old. If it
	  is, delete files in it with ctime older than 36h. However if
	  atime - ctime > 36h, it means that there's nothing to be deleted and
	  the scanning isn't done. We update atime ourself if filesystem is
	  mounted with noatime.
	* base_dir doesn't need to be group-readable, don't force it.
	* mail_read_mmaped setting is deprecated and possibly broken. It's now
	  removed from dovecot-example.conf, but it still works for now.
	* Removed also umask setting from dovecot-example.conf since currently
	  it doesn't do what it's supposed to.

	+ Authentication cache caches now also userdb data.
	+ Added mail_log plugin to log various mail operations. Currently it
	  logs mail copies, deletions, expunges and mailbox deletions.
	- dict quota: messages=n parameter actually changed storage limit.
	- A lot of fixes to handling index files. This should fix almost all
	  of the problems ever reported.
	- LDAP: auth_bind=yes was more or less broken.
	- Saved mails and dovecot-keywords file didn't set the group from
	  dovecot-shared file.
	- Fixed potential assert-crash while searching messages
	- Fixed some crashes with invalid X-UID headers in mboxes
	- If you didn't have a namespace with empty prefix, giving STATUS
	  command for a non-existing namespace caused the connection to give
	  "NO Unknown namespace" errors for all the future commands.