Amend Irssi 0.8.21 entry. Another CVE was assigned.
PR: 216020
Submitted by: Vladimir Krstulja <vlad-fbsd@acheronmedia.com>
Security: CVE-2017-5356
Security: https://vuxml.FreeBSD.org/freebsd/3d6be69b-d365-11e6-a071-001e67f15f5a.html