• HTTP/2 connections now use pollsets to monitor the status of the
  ongoing streams and their main connection.
• Fixed a bug where, without 'H2SerializeHeaders' some errors, such
  as a input timeout, did not produce the correct response.
• Added directove 'H2StreamTimeout' to configure a separate value for HTTP/2
  streams, overriding server's 'Timeout' configuration. [rpluem]
• The HTTP/2 connection state handler, based on an experiment and draft
  at the IETF http working group (abandoned for some time), has been removed.
• H2SerializeHeaders no longer has an effect. A warning is logged when it is
  set to "on". The switch enabled the internal writing of requests to be parsed
  by the internal HTTP/1.1 protocol handler and was introduced to avoid
  potential incompatibilities during the introduction of HTTP/2.
• Removed the abort/redo of tasks when mood swings lower the active
  limit. This probably hurts the server more than it helps. Some
  setup, like proxied connections, can be slow to respond to the
  abort of a connection.
• Fixed input handling for requests without body that nevertheless try
  to read one (e.g. mod_cgid handling) to deliver at least an EOS bucket
  before signalling an EOF.
• A regression in v1.15.24 was fixed that could lead to httpd child
  processes not being terminated on a graceful reload or when reaching
  MaxConnectionsPerChild. When unprocessed h2 requests were queued at
  the time, these could stall. See #212.
• Fixed an issue since 1.15.24 that "Server" headers in proxied requests
  were overwritten instead of preserved. [PR by @daum3ns]