Irssi proxy usage:

First you'll need to have the proxy module installed, either configure
irssi with --with-proxy and do make install, or manually:

  cd src/irc/proxy
  make
  mkdir ~/.irssi/modules
  cp .libs/libproxy.so ~/.irssi/modules/

In irssi, say:

  /LOAD proxy

You really should set some password for the proxy with:

  /SET irssiproxy_password secret

Then you'll need to configure the ports/ircnets the proxy listens in,
something like:

  /SET irssiproxy_ports ircnet=2777 efnet=2778 freenode=2779

There we have 3 different irc networks answering in 3 ports. Note that
you'll have to make the correct /IRCNET ADD and /SERVER ADD commands to
make it work properly.
