- some cleanup and fixes as well, namely simplified RR creation during
  zone load (no malloc)

- RRSet copies removed, packet now stores rrsets directly (structure is
  copied, but copy is shallow)

- use rrset initialization macro instead, or create rrset explicitely

- kept RRSet copies somewhere (node has to create them now)
- replaced knot_rrset_t with knot_rrs_t elsewhere
- semantic checks simplified

- simplified all the functions while I was at it

- Will leak
- Untested

- new types: knot_rr_t and knot_rrs_t
- these can be used in the node structure instead of knot_rrset_t

New Dnssec Tests

Ixfr And Ddns Fixup

This fixes:

* ixfr/add_existing
* ddns/chain

No need to be picky about this, TSIG rcode is 16bit so we might
as well use 16bit number to keep things the same.

This function releases held RCU read lock, so it is possible that
the zone is free in the meantime. To prevent accessing the freed
zone, zone is released after all processing is done and the
pointer is invalidated to prevent further access.

The problem with previous code was that the packet stripped the TSIG
section when it parsed the first IXFR packet from wire. If the code
failed though, the wire was parsed again but this time the TSIG was
already stripped on the wire so the result was garbled data.
I've thrown in some minor cleanup as well.

Zone Create No Lastnode

This makes NSEC3 nodes disappear if it is preceded by a RR with the
same owner and any other record type.

Explained in the test, BIND9 as of 9.9.4 provides wrong closest
encloser wildcard NSEC3 record.

Fix Ddns

Fixes for new tests, tests were modified a bit as well.

Improve Ddns Tests

- Every scenario from old tests rewritten, plus some new ones added, some are still failing

Rrset Free Remove

I'm not sure if this will conflict with some of your work, if yes. we'll cancel this.

- nodes were marked as empty, but the information was never used ...
- renamed one function for clarity.