refs #1360 @30m

* requires parameter -j <NUM> to specify maximum number of parallel zones, like in 'make -j N'
* shows warning if activated

fixes #1282, @2h

fixes #1351, @1h

- If labels are not parsed well, error is returned

Warning: This check was commented as if it was wrong in some case.
         Don't know why and enabling it may cause some problems.

refs #1333 @10m

refs #1333 @15m

fixes #1346 @20m

- May be related to #1215 but was unable to reproduce the issue
  before nor after the changes.

refs #1215 @2h

refs #1203 @1h

refs #1203 @10m

- Was not deleting RDATA at all.
- Since recent changes it tried to delete whole RRSets which was
  wrong (of course, see comments to xfrin_changes_t).
- Keeping track of removed RDATAs, deleting it after successful
  IXFR-in.

refs #1203 @3h

refs #1334 and fixes #1341

fixes #1342