Log Message:
Updated openntpd to 6.0p1.

Changes since OpenNTPD 5.9p1
============================

    * Fixed a link failure on older Linux distributions and a build
      failure on FreeBSD.
    * Set MOD_MAXERROR to avoid unsynced time status when using
      ntp_adjtime.
    * Fixed HTTP Timestamp header parsing to use strptime in a more
      portable fashion.
    * Hardened TLS for ntpd constraints, enabling server name
      verification. Thanks to Luis M. Merino.

Note that HTTPS TLS constraints are currently disabled in pkgsrc pending
evaluation of how best to deal with libressl.