Deadwood snapshot bugfix

I normally don't introduce two Deadwood snapshots in the same day, but I have found and fixed a bug I just introduced.

Basically, the bugfix so we could have answers that are nothing but CNAME records (which was itself a bug introduced by the fix for the "Google bug") introduced another bug: It caused all "this host is not here" answers to be cached for a year.

I've fixed this. See maradns.org/deadwood

This is why reputable software vendors take their time making bug fixes, even security patches available. Often times, a bugfix will introduce other bugs (and, in this case, we have a bugfix introduce another bug, then have the fix for that bug introduce yet another bug).

I understand why DJB basically ended up hating the DNS standard after he was done writing DJBdns.