- QNAME is printed out instead of zone name.

fixes #1413 @5m

- Distinguishing merge in xfrin_apply_add_normal()
  and handling it in xfrin_apply_add().

TODO:
  - Check and fix the same for RRSIGs.

refs #1413 @6h

- Was deleting only the first RDATA in the list.

Fixes leak during IXFR.

- Parsing unknown RDATA (TYPExxx) from packet.
- Parsing IPSECGATEWAY with no gateway item.

This refs #1415, but is strange and should not happen. RRset should be initialized to NULL before calling this function.

- Applies only for some cases now
  - No wildcard child.
  - Closest encloser proof.
- Does not apply for NODATA responses!!!

TODO: clarify and unify.

- Now the function checks if there is some node in the NSEC3 tree.

TODO: Clarify when the zone is considered signed.

- Function for comprehensive comparing serials added to nameserver.
- Added function for loading serials from IXFR query.
- Loading serials before loading changesets in xfr-handler.
- Sending FORMERROR in proper cases after loading changesets
  fails.
- No data in journal results in fallback to AXFR.
- zones_xfr_load_changesets() now leaves changesets empty if the
  slave's serial is equal or larger than the master's serial.
  This results in the IXFR sending function to send out response
  with single SOA.

fixes #1409 @2h

fixes #1374

RETRY events are now deferred until pending transfer is finished
and next RETRY event occurs.

fixes #1400

fixes #1376

fixes #1401

refs #1362 @30m