- Merge PR #420 from dyunwei: DOH not responsing with
  "http2_query_read_done failure" logged.

* nlnet/master:
  Fix NLnetLabs#426: Replace _Py_fopen() with fopen() in pythonmod.c
  - Fix to make tests work with support indicators set for iterator.
  - Fix NLnetLabs#422: IPv6 fallback issues when IPv6 is not properly   enabled/configured.
  Changelog note for PR NLnetLabs#420 - Merge PR NLnetLabs#420 from dyunwei: DOH not responsing with   "http2_query_read_done failure" logged.
  Update netevent.c

clear the c->buffer in the comm_point_send_reply does resolve the "can't fit qbuffer in c->buffer" issue, but it breaks the mesh reply list function that need to reuse the answer. because the c->buffer is cleared in the comm_point_send_reply, it cannot be resued again. it means that it is not inappropriate to clear c->buffer in the comm_point_send_reply.
After some investigation, i found it is appropriate to clear c->buffer before use in the http2_query_read_done.

#420 breaks the mesh reply list function that need to reuse the dns answer.

- Merge PR #517 from dyunwei: #420 breaks the mesh reply list
  function that need to reuse the dns answer.

v1.13.1 has a problem in DoH connection handling.
See NLnetLabs/unbound#420