MFH: r421093
Security update to upstream release 2.1.23.
ChangeLog:
http://bazaar.launchpad.net/~mailman-coders/mailman/2.1/view/1668/NEWS#L8
Security: b11ab01b-6e19-11e6-ab24-080027ef73ec
Security: CVE-2016-6893
Approved by: ports-secteam (delphij@)