v2.2.31 release candidate released

[Timo Sirainen]

https://dovecot.org/releases/2.2/rc/dovecot-2.2.31.rc1.tar.gz
https://dovecot.org/releases/2.2/rc/dovecot-2.2.31.rc1.tar.gz.sig 

Unless new bugs are found, this will be the final v2.2.31 release, which will be released on Monday.

 * LMTP: Removed "(Dovecot)" from added Received headers. Some
   installations want to hide it, and there's not really any good reason
   for anyone to have it.

 + Add ssl_alt_cert and ssl_alt_key settings to add support for
   having both RSA and ECDSA certificates.
 + pop3-migration plugin: Strip trailing whitespace from headers
   when matching mails between IMAP and POP3. This helps with migrations
   from Zimbra.
 + acl: Add acl_globals_only setting to disable looking up
   per-mailbox dovecot-acl files.
 + Parse invalid message addresses better. This mainly affects the
   generated IMAP ENVELOPE replies.
 - v2.2.30 wasn't fixing corrupted dovecot.index.cache files properly.
   It could have deleted wrong mail's cache or assert-crashed.
 - v2.2.30 mail-crypt-acl plugin was assert-crashing
 - v2.2.30 welcome plugin wasn't working
 - Various fixes to handling mailbox listing. Especially related to
   handling nonexistent autocreated/autosubscribed mailboxes and ACLs.
 - Global ACL file was parsed as if it was local ACL file. This caused
   some of the ACL rule interactions to not work exactly as intended.
 - auth: forward_* fields didn't work properly: Only the first forward
   field was working, and only if the first passdb lookup succeeded.
 - Using mail_sort_max_read_count sometimes caused "Broken sort-*
   indexes, resetting" errors.
 - Using mail_sort_max_read_count may have caused very high CPU usage.
 - Message address parsing could have crashed on invalid input.
 - imapc_features=fetch-headers wasn't always working correctly and
   caused the full header to be fetched.
 - imapc: Various bugfixes related to connection failure handling.
 - quota=imapc sent unnecessary FETCH RFC822.SIZE to server when
   expunging mails.
 - quota=count: quota_warning = -storage=.. was never executed
 - quota=count: Add support for "ns" parameter
 - dsync: Fix incremental syncing for mails that don't have Date or
   Message-ID headers.
 - imap: Fix hang when client sends pipelined SEARCH +
   EXPUNGE/CLOSE/LOGOUT.
 - oauth2: Token validation didn't accept empty server responses.
 - imap: NOTIFY command has been almost completely broken since the
   beginning. I guess nobody has been trying to use it.