• Extensive testing in production done by Alessandro Bianchi (@alexskynet)
  on the v2.0.x versions for stability. Many thanks!
• refactored stream response handling to reflect the different phases
  (response/data/trailers) more clearly and help resolving cpu busy loops.
• Adding more negative tests for handling of errored responses to cover
  edge cases.
• mod_http2: fixed handling of response where neiter an EOS nor an ERROR was
  received as a cause to reset the stream.
• mod_proxy_http2: generating error buckets for fault response bodies, to
  signal failure to fron when response header were already sent.