irc/irrsi: Update to 1.2.1

• Fixes security vulnerability when using SASL for login that might suddenly fail in some cases (CVE-2019-13045). [1]
• It also fixes issues with input line echoing of UTF-8 chars with non UTF-8 terminals. [2]

Changelog:

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

PR: 238892 [1], 238591 [2]
Submitted by: Santhosh Raju [1], Victor Sudakov [2]
Approved by: David O'Rourke (maintainer)
MFH: 2019Q2
Security: 475f952c-9b29-11e9-a8a5-6805ca0b38e8