darcs inputs, URL inputs, minor fixes

- darcs: I have added a test, everything should basically work; the sql file may need a rename to a number, but I kept getting conflicts on it
- URLs: you need this if you e.g. want to build VM images from up-to-date repositories
- some characters that are currently disallowed in various places are harmless, and pop up in some builds
- xsltproc is happy to crunch big logs for dozens of minutes even though the session will certainly time out by then

All these patches are "live" at http://divine.fi.muni.cz/hydra