Log Message:
Update to 4.2.2

* Readd _OPENBSD_SOURCE explicitly to fix build on NetBSD 9

Changelog:
13 August 2019: Wouter
	- Fix error message for out of zone data to have more information.

12 August 2019: Wouter
	- Fix #33: Fix segfault in service of remaining streams on exit.

6 August 2019: Wouter
	- Tag for 4.2.2rc1.

5 August 2019: Wouter
	- PR #31: nsd-control: Add missing stdio header.
	- PR #32: tsig: Fix compilation without HAVE_SSL.
	- Cleanup tls context on xfrd exit.

31 July 2019: Wouter
	- Fix #29: SSHFP check NULL pointer dereference.
	- Fix #30: SSHFP check failure due to missing domain name.
	- Fix to timeval_add in minievent for remaining second in microseconds.

22 July 2019: Wouter
	- Set timeout for refetch immediately, only spread load when there
	  are retries.

19 July 2019: Wouter
	- Set no renegotiation on the SSL context to stop client
	  session renegotiation.

18 July 2019: Wouter
	- Fix #25: NSD doesn't refresh zones after extended downtime,
	  it refreshes the old zones, with a random delay of a couple of
	  seconds to spread the load.
	- Fix so that expired zones stay expired when server is down a
	  long time.

17 July 2019: Wouter
	- Fix that NSD warns for wrong length of the hash in SSHFP records.

15 July 2019: Wouter
	- PR #23: Fix typo in nsd.conf man-page.

4 July 2019: Wouter
	- Set version to 4.2.2 in development.
	- clean memory on exit of nsd-checkzone for memory debug.
	- Fix #20: CVE-2019-13207 Stack-based Buffer Overflow in the
	  dname_concatenate() function.  Reported by Frederic Cambus.
	  It causes the zone parser to crash on a malformed zone file,
	  with assertions enabled, an assertion catches it.
	- Fix #19: Out-of-bounds read caused by improper validation of
	  array index.  Reported by Frederic Cambus.  The zone parser
	  fails on type SIG because of mismatched definition with RRSIG.

2 July 2019: Wouter
	- Tag for 4.2.1rc1

27 June 2019: Wouter
	- Fix unit test for added options and no dot after zone updated
	  log message.
	- Fix compile without accept4.

21 June 2019: Wouter
	- Omit remaining tcp processing if the list is empty.
	- Fix output of nsd-checkconf -h.

20 June 2019: Wouter
	- Initialize event structures before event_set, to stop uninitialized
	  values from setting event library lists and assertions, that would
	  sometimes also show after event_del.
	- Added num.tls and num.tls6 stat counters.
	- PR #12: send-buffer-size, receive-buffer-size,
	  tcp-reject-overflow options for nsd.conf, from Jeroen Koekkoek.
	- Do not use symbol from libc, instead use own replacement, if not
	  available, for accept4.
	- Fix #14, tcp connections have 1/10 to be active and have to work
	  every second, and then they get time to complete during a reload,
	  this is a process that lingers with the old version during a version
	  update.

19 June 2019: Wouter
	- Fix tls handshake event callback function mistake, reported
	  by Mykhailo Danylenko.

18 June 2019: Wouter
	- Fix #15: crash in SSL library, initialize variables for TCP access
	  when TLS is configured.

14 June 2019: Wouter
	- Fix to init event not pointer, in reassignment.

12 June 2019: Wouter
	- Fix to init event structure for reassignment.