Patch to use a ThreadPool in TCPSession

I've posted a patch to use a ThreadPool for processNextFrame() in
TCPSession. It uses the concurrent.jar library. It seems to improve things
on my Linux box, the CPU usage drops, new processes aren't created, and the
I/O rate seems to improve. It's a bit of a noddy patch but any thoughts
anybody. I couldn't see any problems it might create, but I don't know the
core internals.