replace remaining gethostby*() calls with Net::DNS calls.  (better
error reporting)

compare serial number of zone transfer data and report differences

Check RP records that they point to a TXT record.

Check for CNAME and other data.  (modern BIND versions disallow this,
but not everyone sadly is up to date)

Check parent delegation (a la doc) and check for lame delegations.
Compare serial numbers of all NS servers and report differences.
(a la doc)

./dnswalk non-existant.domain doesn't generate a very useful message

complete RFC 1101 check.. A records in rev file