Added cchafe's fixes to hubpatch mode 2 from main branch.
Some minor cleanup to the UdpDataProtocol code and comments.

There were still some minor threading issues with the previous approach, so have gone back to sharing a full duplex socket with a QUdpSocket object created only for reading. (Writing is done directly to the socket.) Seems to work consistently on all platforms. Have also merged some platform specific code where separate branches are no longer necessary. (This requires Vista or later when running on Windows.)

Finally managed to test on windows, and it did not go well. It seems that either windows sockets or the way that QUdpSocket manages them is not as thread safe as POSIX sockets. It worked when running as a client, but crashed out after about a second as a server. Also, no combination of half closing sockets (the old way of doing it) seemed to work consistently across both IPv4 and IPv6 on all platforms.

So, have moved to sharing a single QUdpSocket object between both the sender and receiver, locking when a read or write is taking place. (Am not currently locking when checking if there are available datagrams, and that doesn't seem to be causing any trouble.)

Revert of last changes (apart from string copy) - worked on OS X but not Linux.

Make sure we copy the mPeerAddress string before modifying it to set the client name. 
Simplified IPv6 implementation. (Managed to get it working using the old model, so JackTrip.cpp doesn't need to pass a single socket between threads.)

Allow -z option to work in server hub mode. Enable DNS lookups when connecting as a hub client.

Added IPv6 support. (Not tested on Win32 yet, but necessary OS specific changes have been made.) The trick of binding two sockets to the same port by shutting down write capabilities on one of them didn't work as expected on IPv6. So instead, a single full duplex socket is shared by two half duplex QUdpSocket objects.

rename port variable almost ready, still need to sort input to functions and rename global port numbers