websocket client library

websocket client library

This introduce 2 files for creating client
of websockets x-afb-json1:
 - afb-wsj1.c
 - afb-ws-client.c

The file afb-wsj1.c implements the protocol
x-afb-json1 on top of afb-ws.c.
It could be used to rewrite afb-ws-json1.

The file afb-ws-client.c implements a
light version of the websocket handshaking
to open a afb-wsj1 based on an uri.

Change-Id: Ie53a3b4ff91a9efac32b667b57f8005266db6001
Signed-off-by: José Bollo <jose.bollo@iot.bzh>