New redirector

FYI - I've committed a new version of the URL redirector for downloads.

The old version was being used for linkfilter-breakthrough to distribute
viruses :-(

Since I was hacking around that code anyway, I didn't just add a filter
to it, but changed around how it works a bit. Apart from it no longer
being possible to use it to break through stupid linkblockers, it has
also made the URLs easier to read and copy/paste, and we're also storing
the logging information in a way that's much easier to analyze than before.

Do keep your eyes open for bugs, of course :-)

//Magnus