Must close connection on masked server->client frame

[gimite]

http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-17#section-5.1

A client MUST close a connection if it detects a masked frame.

Related: #102

[ranc]

In WebSocket.as line 491, add:
if (buffer[1]>127)
{
dispatchCloseEvent(false, 1002, "Server must not mask.");
return null;
}

[gimite]

Thanks. Pulled at 1402307