Allow TLS connections (and other)

[nealey]

The :connect-function parameter in rcirc-alist can be specified to provide a function compatible with open-network-stream. Here are some examples:

(defun open-tls-cert-stream (name buffer host service)
  (start-process name buffer
               "socat" "STDIO" (concat "OPENSSL:" host ":" (int-to-string service)
                                       ",cert=~/certs/private/irc.key"
                                       ",cafile=~/certs/snakeoil.pem")))
'(("irc.frobozz.net" :port 6697 :connect-function open-tls-stream)
  ("irc.frotz.gue" :port 994 :connect-function open-tls-cert-stream))