WebSocket connections allow web-based clients to connect to IRC. This
commit implements the WebSocket sub-protocol as specified by the pending
IRCv3 proposal [1].
WebSocket listeners can now be set up via a "wss" protocol in the
`listen` directive. The new `http-origin` directive allows the CORS
allowed origins to be configured.
[1]: https://github.com/ircv3/ircv3-specifications/pull/342
git-svn-id: file:///srv/svn/repo/suika/trunk@323 f0ae65fe-ee39-954e-97ec-027ff2717ef4
f38af41317