Revision 1717016

* buckets/split_buckets.c
  (serf_split_destroy): Clear some values.

* protocols/http2_protocol.c
  (http2_write_data): Clear some state.
  (serf_http2__ensure_writable): Fix edge case to avoid endless loop.

* protocols/http2_stream.c
  (serf_http2__stream_pre_cleanup): Properly clear data_tail.
  (serf_http2__stream_cleanup): Really stop destroying data_tail.
  (stream_send_data): Mark stream closed when done. Ensure write again in
    all cases where we have to write again.