Python concurrency

Part of the reason why pjs pjabberd only works on a single processing unit (core) right now is because of the GIL in Python. The architecture uses the asyncore module (asynchronous, like twisted). Looks like it was a good choice, though. In Concurrency with Python, Twisted, and Flex Bruce Eckel demonstrates how he got extreme parallelism from Python+Twisted by spawning n python interpreters, where n is the number of processing units on a machine, and communicating between them via sockets. The Flex part can be mostly ignored. This will come in handy for pjabberd when we add support for multiprocess operation and clustering.