Configure libidn

(ported 3b5b0f64)

512B limit for a single log line

Interface list could be changed before the threads finish reading
it. This code simply waits for the readers before publishing, but
a smarter queueing is going to be done in #239.

The jobs are removed from the task queue and executed afterwards,
cannot synchronize on the queue only.

- event_dispatch checks for frozen events
- event_cancel must be called outside of the events lock,
as the event itself locks it as well

This Is Pragmaaa!

DNSSEC: key rotation fixes

We need to keep unused keys (not-public, inactive) in the zone keys
list, because we need the timestamps for correct planning of rollover.

The capacity of the list is unlimited (unexpected in real-world).

- changesets.c
- contents.c - just removed debug code

Strl functions

 - cov #1216800