Simple prototype for a DNS query logger. The idea is to feed a zone
into libpcap monitor, and it will maintain the 'lastseen' timestamp
and a hitcount for each entry in the zone.

The purpose of this is to determine which zone entries are obsolete,
so that they can be removed with confidence that they are not used.
How long to monitor before concluding that the entry is obsolete, is
up to the administrator.

These numbers can then be exported by sending a HUP, which will save
to a text file named 'dns.state' in the cwd of the process. This file
can in turn be run through further processing, for example insertion
into an sql database.

Creating the initial record list:

rndc dumpdb -all
grep -E "IN[[:space:]]+(A|CNAME|AAAA|CNAME|MX|PTR)" \
/var/lib/bind/named_dump.db > records.txt