[Dovecot] NONEXISTENT handling

As of 2.0.12, looks like NONEXISTENT response code isn't working
properly again. Previously brought up issues relating to this here:
http://markmail.org/message/jxbgdfv26pws66og

With a nonexistent mailbox "FOO", I see this:

1 DELETE "FOO" 1 NO Mailbox doesn't exist: FOO // Should be: 1 NO [NONEXISTENT] Mailbox doesn't exist: FOO

2 RENAME "FOO" "BAR" 2 NO Mailbox doesn't exist: FOO // Should be: 2 NO [NONEXISTENT] Mailbox doesn't exist: FOO

michael