mail/cyrus-imapd34: Add Cyrus imapd version 3.4.6

IMAP (Internet Message Access Protocol) is an Internet standards-track
protocol for accessing messages (mail, bboards, news, etc). The Cyrus
IMAP server differs from other IMAP server implementations in that it
is generally intended to be run on "sealed" servers, where normal users
are not permitted to log in. The mailbox database is stored in parts of
the filesystem that are private to the Cyrus IMAP system. All user
access to mail is through the IMAP, POP3, or KPOP protocols.

Version 3.4.x of the Cyrus IMAP server is a useful transition version
from 2.4.x to higher versions, since this is the latest version that
can upgrade in-place from Cyrus IMAP 2.4. Once upgraded to 3.4, you can
then consider upgrading to later versions.