* lisp/net/rcirc.el: Add support for SSL/TLS connections.

* lisp/net/rcirc.el: Add support for SSL/TLS connections.
(rcirc-server-alist): New field `encryption'.
(rcirc): Check `encryption' settings.
(rcirc-connect): New arg `encryption'.  Use open-network-stream.
Merge make-local-variable into `set'.
(rcirc--connection-open-p): New function.
(rcirc-send-string, rcirc-clean-up-buffer): Use it to handle case where
the process is not a network process (e.g. running gnutls-cli).
(set-rcirc-decode-coding-system, set-rcirc-encode-coding-system):
Make rcirc-(en|de)code-coding-system local here.
(rcirc-mode): Merge make-local-variable into `set'.
(rcirc-parent-buffer): Make permanent buffer-local.
(rcirc-multiline-minor-mode): Don't do it here.
(rcirc-switch-to-server-buffer): Don't switch to a random buffer if
there's no server buffer.