nsd: Update to 4.6.0

Changelog:
This release adds the zone verification support from the CreDNS code.
There are also some bug fixes in the ixfr out code.

Zone verification can start a verifier program that reads the new zone
data. It can reject the update. Or process the new zone data. The intent
is for a DNSSEC verifier to inspect the zone before it is passed on with
zone transfer or served to clients.

The zone verification can be enabled with enable: yes in the verify
section in nsd.conf. You can then list the interfaces the NSD listens on
while the verifier is active, so it can send queries for the new zone
contents. With verify-zones: yes zones are verified by default. The
command that is executed can be set with the verifier: ldns-verify-zone
option. With verifier-count the max number of concurrent verifiers can
be set. With the verifier-feed-zone: yes option the zone can be input
on stdin to the verifier program. A timeout to stop the verifier can be
set with the verifier-timeout option.

Per zone options can also be set for a pattern or for a zone, for zone
verification. With verify-zone the zone verification can be enabled
per zone. The verifier can be set per zone. And the verifier-feed-zone
and verifier-timeout options can be controlled per zone.

FEATURES:
    Port zone-verification from CreDNS to NSD4.

BUG FIXES:
    Fix static analyzer reports on ixfrcreate temp file.
    Fixup wrong ixfrcreate fread return check.


(ryoon)