irc/irssi: Update to 1.1.2

Changelog: https://irssi.org/NEWS/#v1-1-2

Irssi Security Advisory: https://irssi.org/security/irssi_sa_2019_01.txt

PR: 234798
Submitted by: David O'Rourke <dor.bsd@xm0.uk> (maintainer)
Submitted by: tj@mrsk.me (email)
MFH: 2019Q1