Log Message:
irssi: update to 0.8.20, security fix.

catch up with irssi-icb, irssi-xmpp distinfo (they grab irssi versioned
file).

comment out part of irssi-xmpp makefile which is breaking the build.

irssi 0.8.20 changes:

	- Correct the name of an emitted sasl signal (#484)
	- Correct the prototype for the 'message private' signal (#515)
	- Corrections in away and hilight help text (#477, #518)
	- /squery and /servlist commands have been restored.
	- Where Irssi would previously only report "System error" on connect,
	  it will now try harder to retrieve the system error message.
	- Fixed issue with +channels not working properly (#533)
	- Fixed crash in optchan when item has no server (#485)
	- Fixed random remote crash in the nicklist handling (#529)
	- Fixed remote crash due to incorrect bounds checking on
	  formats, reported by Gabriel Campana and Adrien Guinet from
	  Quarkslab.