• not counting file buckets again stream max buffer limits.
  Effectively transfering static files in one step from slave to master
  connection.
• mod_http2: comforting ap_check_pipeline() on slave connections
  to facilitate reuse (see #128).
  [reported by Armin Abfalterer]
• mod_http2: http/2 streams now with state handling/transitions as defined
  in RFC7540. Stream cleanup/connection shutdown reworked to become easier
  to understand/maintain/debug. Added many asserts on state and cleanup
  transitions.