Allow the CSTP layer to operate without TLS

That also introduces a unix domain socket under which connections to the
server can occur.

src/ocserv-args.def

@@ -124,6 +124,10 @@ max-same-clients = 2
 tcp-port = 3333
 udp-port = 3333
 
+# Accept connections using a socket file. The connections are
+# forwarded without SSL/TLS.
+#unix-conn-file = /var/run/ocserv-conn.socket
+
 # Keepalive in seconds
 keepalive = 32400