• reworked connection state handling. Improved scoreboard update (server-status).
  Default on H2KeepAliveTimeout same as H2Timeout, 5 seconds. After that,
  connections are closed.
  On asynchronous MPMs (event), keep-alive connections no longer block threads,
  but exact timeout handling is then up to the MPM. In these MPMs, having a
  longer H2KeepAliveTimeout may be suitable.
• new CGI environment variables HTTP2 and H2PUSH. With former "on", the
  connection uses HTTP/2. With latter "on", the request may trigger Server Push
  via Link headers, as both server and clients support it.