Prevent clearing of client.request and client.response for XHR and JSONP polling

[danielbeardsley]

When listening to the client 'connect' message, clients using the XHR and JSONP polling protocols have no request or response attribute so I can't get access to the cookies. With both of these protocols, calling _write() calls onClose() and clears the requrst and response variables. I've just made a change that keeps these around until the next request, so request.headers.cookies is still available. Not sure if this is appropriate for the official repo, but it worked for me.

socket.on('connection', function(client){
  // client.request and client.response are both null
});

[rauchg]

We'll expose normalized information directly through a public API (decoded cookies, extraHeaders, remoteAddress). This will apply to all clients from all transports. extraHeaders will contain stuff that is not available to all transports, but might be useful (eg: user-agent not available on websocket)