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

{
    std::string port = strprintf("%u", GetListenPort());
    const char * multicastif = nullptr;
    const char * minissdpdpath = nullptr;
    struct UPNPDev * devlist = nullptr;
    char lanaddr[64];
    int error = 0;
#if MINIUPNPC_API_VERSION < 14
    devlist = upnpDiscover(2000, multicastif, minissdpdpath, 0, 0, &error);
#else
    devlist = upnpDiscover(2000, multicastif, minissdpdpath, 0, 0, 2, &error);
#endif
    struct UPNPUrls urls;
    struct IGDdatas data;
    int r;
    r = UPNP_GetValidIGD(devlist, &urls, &data, lanaddr, sizeof(lanaddr));
    if (r == 1)
    {
        if (fDiscover) {
            char externalIPAddress[40];
            r = UPNP_GetExternalIPAddress(urls.controlURL, data.first.servicetype, externalIPAddress);
            if (r != UPNPCOMMAND_SUCCESS) {
                LogPrintf("UPnP: GetExternalIPAddress() returned %d\n", r);
            } else {
                if (externalIPAddress[0]) {
                    CNetAddr resolved;