mod_lua: Add rudimentary WebSocket support. This is a WIP (emphasis on the W, I and P) and subject to change as the idea surrounding it evolves into something meaningful. But for now, WebSockets, yay! Please do review this!

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1522030 13f79535-47bb-0310-9956-ffa450edef68