New port: dns/nsec3walker: Walk NSEC3 secured DNSSEC zones

Installing current DNSSEC (NSEC3) exposes private DNS data to low-cost
DNS database espionage. The nsec3walker tool allows administrators and users
to see how much private information is being given away by DNSSEC.

WWW: https://dnscurve.org/nsec3walker.html

PR: 215995
Submitted by: Piotr Kubaj <pkubaj@anongoth.pl>