Log Message:
nghttp2: updated to 1.38.0

lib
This release fixes the bug that on_header callback is still called after stream \ 
is closed.

third-party
http-parser is upgraded to v2.9.1.

nghttpx
This release fixes the bug that authority and path altered by per-pattern mruby \ 
script can affect backend selection on retry.
It also fixes the bug that HTTP/1.1 chunked request stalls.
Now nghttpx does not log authorization request header field value with -LINFO.
Now nghttpx can be built with modern LibreSSL.