Log Message:
Update to Dovecot 2.0.16.

* VSZ limits weren't being enforced for any processes. On server with
  large mailboxes you may now see errors about it if the limits aren't
  high enough. To fix them, either increase individual service {
  vsz_limit } values or simply increase the default_vsz_limit setting.
* Proxying: If using ssl=yes or starttls=yes with a hostname (not IP)
  as proxy destination, require that the certificate matches the given
  hostname.
* LMTP: Changed default client_limit to 1. This should improve LMTP
  throughput with default settings.
* dsync: Quota is no longer enforced (i.e. dsync can't fail because
  user is over quota).

+ Added "auto" mail storage driver, which can be used to autodetect
  mailbox location and format. This behavior is already the default
  for empty mail_location setting, so this change is mainly useful for
  shared namespace's location setting.
+ checkpassword: Export all auth %variables to AUTH_* environment.