Added irc-api r181 (+ slf4j 1.7.5)

IRC client library irc-api.
License: Apache License 2.0
http://code.google.com/p/irc-api

SLF4J logging facade 1.7.5
License: MIT
http://www.slf4j.org/

irc-api uses slf4j logging facade for its logging operations. We
use the API and JDK14 implementation in order to connect to the
existing logging backend of Jitsi.