To be able to label incoming tor connections as different from normal localhost connections in e.g. `getpeerinfo` and the peers list in the GUI it'd be useful to have them connect on an alternative local-only port. Or even better, a UNIX socket.

For manually set-up hidden services this would have to be configured manually and could add a `hsport` option or such. The external port would still appear as `XXXXXXXXX.onion:8333`, however internally it would redirect to a that port.

In the case of `torcontrol` this would be easy to set up automatically. It could add a new (localhost) binding port automatically and this code would have to be changed:
- https://github.com/bitcoin/bitcoin/blob/master/src/torcontrol.cpp#L441
- https://github.com/bitcoin/bitcoin/blob/master/src/torcontrol.cpp#L477

{
public:
    typedef std::function<void(TorControlConnection&)> ConnectionCB;
    typedef std::function<void(TorControlConnection &,const TorControlReply &)> ReplyHandlerCB;
    /** Create a new TorControlConnection.
     */
    explicit TorControlConnection(struct event_base *base);
    ~TorControlConnection();
    /**
     * Connect to a Tor control port.
     * target is address of the form host:port.
     * connected is the handler that is called when connection is successfully established.
     * disconnected is a handler that is called when the connection is broken.
     * Return true on success.
     */
    bool Connect(const std::string &target, const ConnectionCB& connected, const ConnectionCB& disconnected);
    /**
     * Disconnect from Tor control port.
     */
    void Disconnect();
    /** Send a command, register a handler for the reply.
     * A trailing CRLF is automatically added.
     * Return true on success.
     */