Update to Dovecot 2.1.5

* IMAP: When neither the session nor the mailbox has modseq tracking enabled,
  return the mailbox as having NOMODSEQ in SELECT/EXAMINE reply. Old versions
  in this situation always simply returned HIGHESTMODSEQ as 1, which could have
  broken some clients.

+ dict file: Added optional fcntl/flock locking (default is dotlock)
+ fts-solr: doveadm fts rescan now resets indexes, which allows reindexing
  mails. (This isn't a full rescan implementation like fts-lucene has.)
+ doveadm expunge: Added -d parameter to delete mailbox if it's empty after
  expunging.
- IMAP: Several fixes related to mailbox listing in some configs
- director: A lot of fixes and performance improvements
- v2.1.4 didn't work without a mail home directory set
- mbox: Deleting a mailbox didn't delete its index files.
- pop3c: TOP command was sent incorrectly
- trash plugin didn't work properly
- LMTP: Don't add a duplicate Return-Path: header when proxying.
- listescape: Don't unescape namespace prefixes.


(ghen)