de471c4655
Currnetly conn_ctrl_init() does an fd_insert() and conn_ctrl_close() does an fd_delete(). These are the two only short-term obstacles against using a non-fd handle to set up a connection. Let's have pur these into the protocol layer, along with the other connection-level stuff so that the generic connection code uses them instead. This will allow to define new ones for other protocols (e.g. QUIC). Since we only support regular sockets at the moment, the code was placed into sock.c and shared with proto_tcp, proto_uxst and proto_sockpair.