Revision 1716854

Move the stop-writing handling (for ssl negotiate states) to the connections,
to avoid having to look at these in each protocol case.

* incoming.c
  (serf__process_client): Introduce here.

* outgoing.c
  (read_from_connection): Move from here...
  (process_connection): ... to here.

* protocols/http2_protocol.c
  (http2_outgoing_read,
   http2_incoming_read): Remove here.