API for binding QTcpSockets to specific local port without using QTcpSocket::setSocketDescriptor()

It would be convenient if QTcpSocket supported binding to a local port; it's possible at the moment for the user to do by getting the socket descriptor and operating on it directly, but a Qt API would be preferrable.

Also good suggestions:

• binding to a local address (not just a port)
• if possible, take a QNetworkInterface to indicate the address(es) to bind to.