3.7.0 - 2021-06-08
    * TCP threads now shut down faster on daemon stop/replace with active
      connections; previously they took up to 10s in a two-phased shutdown
      approach, now they take up to 5s in a single phase.
    * TCP threads' timeout management fudge factor for coalescing timer events
      from multiple connections was increased from 100ms to 250ms.
    * The UDP send-side code is now non-blocking; it will immediately fail for
      lack of SO_SNDBUF space for the response instead of blocking up to ~257ms
      in an attempt to wait for for buffer availability.  This has less chance
      of negatively impacting other requests waiting in the receive buffer
      during short spikes, at the cost of burning a little more CPU (to create
      answers which are quickly dropped on the output side) when buffers are
      overwhelmed with traffic.
    * Control sock proto now documented (imperfectly!) at docs/ControlSock.md
    * Control sock clients now send their version in REQ_INFO
    * Clearer messaging about certain corner-case configuration parser failures
      related to bad DNS escapes and $include files.
    * Bugfix for parsing zonefiles > 4GiB in size
    * Some possible race conditions in the testsuite which could cause false
      failures were fixed
    * Various internal refactorings and code QA improvements