TLS encryption not handled if required by server

[hocken]

TLS encryption is not handled by the gateway when the starttls feature is required by the XMPP server.

In order to communicate with servers that require encryption, the gateway should buffer the server's response that includes the initial opening stream tag and the first feature list. If

<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'><required/></starttls>

is included in the feature list, the gateway must

1. perform the TLS handshake,
2. upgrade the socket, and
3. re-open the stream.
   Then the first feature list with the starttls feature must be dropped and the lately received feature list with the entry requiring SASL authentication must be forwarded to the client. Of course in that case the wss:// scheme should be used to provide encryption between client and gateway as well.