MusicMUD release

You can now download MusicMUD 2.1. This is the codebase we are currently running (with a few improvements) but with Cryosphere-specific stuff cut out, and a small demonstration world. At the moment comes with very patchy docs indeed (so will only be of use to people who have previously built for Cryo), but this will be fixed at some point.

later: We've moved earlier: IPv6