WIP: Changes to recognise upgrade request for RFC 6455

I've made changes so that the upgrade request is now no longer case sensitive as per the advice in [issue 7](https://github.com/superfeedr/ejabberd-websockets/issues/7#issuecomment-3568078).

However, Chrome 16 still does not work. Further changes are required to make this compatible with [RFC 6455](http://tools.ietf.org/html/rfc6455) ([as implemented by FF11 and Chrome 16](http://en.wikipedia.org/wiki/WebSocket#Browser_support)).

Posting this purely as work in progress, but hopefully it will help.

The logs from ejabberd now look like:

    =INFO REPORT==== 2012-01-20 13:38:50 ===
    ERROR: "D(~p:~p:~p) : Request data:~p:~n" - [<0.382.0>,
                                                                         mod_websocket,
                                                                         36,[],
                                                                         {wsrequest,
                                                                          [{"Sec-WebSocket-Version",
                                                                            "13"},
                                                                           {"Sec-Websocket-Key",
                                                                            "j34gc9D6Hl6qnl0Pz7Ai+w=="},
                                                                           {"Sec-WebSocket-Protocol",
                                                                            "xmpp"},
                                                                           {"Origin",
                                                                            "null"},
                                                                           {'Host',
                                                                            "xmpp.local:5288"},
                                                                           {'Connection',
                                                                            "Upgrade"},
                                                                           {'Upgrade',
                                                                            "websocket"}],
                                                                          undefined,
                                                                          false,
                                                                          'GET',
                                                                          ["ws-xmpp"],
                                                                          #Port<0.3190>,
                                                                          gen_tcp,
                                                                          undefined}]

    =INFO REPORT==== 2012-01-20 13:38:50 ===
    D(<0.382.0>:mod_websocket:49) : Origin is valid.

    =INFO REPORT==== 2012-01-20 13:38:50 ===
    D(<0.382.0>:ejabberd_websocket:184) : Websocket!