Add secure method to tcp socket for firefox

Adding a secure method to tcp socket for firefox.

Firefox sockets can be upgraded to TLS using by calling nsISocketTransportService.createTransport with type 'starttls' and the same hostname and port as an existing insecure tcp socket.  Documentation is here: https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/Reference/Interface/nsISocketTransportService#createTransport()

Tested by connecting to chat.facebook.com on port 5222, then upgrading the socket to TLS, and verifying we get prompted with a challenge from facebook in response.