- Added more detailed debug messages to zone-diff

- In IXFR/AXFR processing replaced rrset_merge() by
  rrset_merge_no_dupl().
- In some other cases it is not reuqired.
- Modified rrset_compare() function to not check TTL
  TODO: check if this doesn't cause problems elsewehere.
- Needs some testing.

refs #1953 @20m

- If all RDATA have been removed from a RRSet, but the RRSet was
  not removed because RRSIGs remained, and new RDATA added to this
  RRSet had different TTL, the TTL from the old RRSet was used.
  This was fixed by rewriting the TTL by the TTL fo the new RRSet.

refs @1963 @30m

+ Some minor fixes.

refs #1949

- Even to non-API functions.
- Removed duplicated function.

refs #1949

Refs #1949

- Added KNOT(D)_ENODIFF, which is now being returned when no zone diff could be produced.
- if new zone has lower serial than old zone, return KNOT_ERANGE
- Proper comparison of serials added.

Refs #1949

Refs #1949

- Replaced error codes (KNOT -> KNOTD)

Refs #1949

- To zones.c
- Also saves changesets to journal, journal reference is taken from the first zone.

refs #1961 @15m

+ Small fix to search for a RRSet in a packet.

- Checking if the given dname is not NULL.

- Moved a comment in zone-contents.c

Refs #1953 @3h

Refs #1956

Refs #1956 @2h

+ Fixed freeing of new RDATA in IXFR rollback.

refs #1952 @30m

regs #1952 @20m

- If there was only one RDATA in the new RRSet, it wasn't freed.

refs #1952 @20m