- auth: If userdb lookup fails internally, don't cache the result.
- Added support for userdb lookup to fail with a reason
- sdbox: mailbox_update() could have changed UIDVALIDITY incorrectly
- layout=maildir++: Fixed deleting mailboxes with mailbox=file storages
- Fixed potential problems with parsing invalid address groups.
- dsync: Don't repeatedly try to keep opening the same failing mailbox
- lib-storage: Don't crash if root mail directory isn't given.
