2.3.1 - 2018-02-15
    * GeoIP2: Detect coordinate-free post-2018 GeoLite2-City databases, and
      refuse to use them with auto_dc_coords. cf:
      https://blog.maxmind.com/2018/01/02/discontinuation-of-the-geolite-legacy-databases/
    * GeoIP2: fixed the handling of automatic, coordinate-based mapping for
      networks with no coordinates (e.g. anon-proxy, satellite).  These now
      return the default datacenter ordering as documented, which is how GeoIP1
      has always behaved.  The GeoIP2 code was calculating distances for these
      networks based on literal 0,0 coordinates since the code was introduced.
    * Removed illegal malloc function attributes (could cause optimizer bugs?
      no known reports)
    * Removed useless/invalid syslog.target dependency from systemd unit
    * Fix testsuite breakage with system Net::DNS
    * Various minor code-quality / docs / logs / errmsg / spelling fixups