[Dovecot] v2.1.13 released

http://dovecot.org/releases/2.1/dovecot-2.1.13.tar.gz http://dovecot.org/releases/2.1/dovecot-2.1.13.tar.gz.sig

    - Some fixes to cache file changes in v2.1.11.
    - fts-solr: Overlong UTF8 sequences in mails were rejected by Solr and
      caused the mails to not be indexed.
    - virtual storage: Sorting mailbox by from/to/cc/bcc didn't work.