mod_h2 v0.8.0

• when serving static files, these are kept open longer (and buffer copied
  less). Use config "H2SessionExtraFiles" to change the value. The more you
  can give per connection, the better. But you may run out of open file
  handles, if not careful. Default value is 5, which seems to work on my
  config with mpms worker, event and prefork. Basically, eaach httpd process
  needs at least #connections + #workers + (#conn * #extrafiles) available.
• main connection buffering, buffer sizes and write sizes are configurable,
  see README.md for the list of options. buffer sizes and write sizes influence
  the TLS performance. Defaults seem reasonably, but ymmv.
• general performance improved due to better handling of stream close and
  resource cleanup
• prefork mpm confirmed working. Unless configured otherwise, each session
  will only have 1 worker thread. Raise this with "H2MaxWorkers"
• changed sandbox cipher config to mozilla recommendation (thanks Lucas)
• sandbox update to nghttp2 1.0.5