Update to 4.2.0

Changelog:
4.2.0
================
FEATURES:
- Print IP address when bind socket fails with error.
- Fix #4249: The option hide-identity: yes stops NSD from responding
  with the hostname for chaos class queries.  Implements the RFC4829
  security considerations.
- Patch to add support for TCP Fast Open, from Sara
  Dickinson (Sinodun).
- Patch to add support for tls service on a specified tls port,
  from Sara Dickinson (Sinodun).
- Use travis for build check, initial unit test and clang analysis.
BUG FIXES:
- Fix to delete unused zparser.default_apex member.
- Fix that the TLS handshake routine sets the correct event to
  continue when done.
- Fix that TLS renegotiation calls the read and write routines again
  with the same parameters when the desired event has been satisfied.
- Fix that TCP Fastopen has better error message and supports OSX.
- Fix to avoid buffer alloc with global buffer in tls write handler.
- Fix to initialize event structure when accepting TCP connection.
- Disable TLS1.0, TLS1.1 and weak ciphers, enable
  CIPHER_SERVER_PREFERENCE, patch from Andreas Schulze.
- further setup ssl ctx after the keys are loaded, for ECDH.
- TLS OCSP stapling support, enabled with tls-service-ocsp: filename,
  patch from Andreas Schulze.
- Fix #10: Fix memory leaks caused by duplicate rr and include
  instructions.
- Fix to define _OPENBSD_SOURCE to get reallocarray on NetBSD.

4.1.27
================
FEATURES:
- Deny ANY with only one RR in response, by default.  Patch from
  Daisuke Higashi.  The deny-any statement in nsd.conf sets ANY
  queries over UDP to be further moved to TCP as well.
  Also no additional section processing for type ANY, reducing
  the response size.
- Fix #4215: on-the-fly change of TSIG keys with patch from Igor, adds
  nsd-control print_tsig, update_tsig, add_tsig, assoc_tsig
  and del_tsig.  These changes are gone after reload, edit the
  config file (or a file included from it) to make changes that
  last after restart.
BUG FIXES:
- Fix #4213: disable-ipv6 and dnstap compile error.
- Fix to reduce region_log_stats if condition, this removes a
  debug statement.
        - Fix for FreeBSD port with dnstap enabled.
- Fix to remove unused code.
- Fix #6: nsd-control-setup: Change validity time to a shorter
  period (<2038).
- Fix unused definition in header remote.h.
- Fix #4236: IPV4_MINIMAL_RESPONSE_SIZE=1480 is slightly too big.
- Fix #4235: IP_PMTUDISC_OMIT on IPv4/UDP sockets.
- Fixed radtree_insert memory leak.
- Fixed access recycled variable.

(ryoon)