Netconf monitoring RFC 6022 Sessions (https://github.com/clicon/clixon/issues/370)

- statistics and transport/source-host parameters
  - extended internal NETCONF hello with transport and source-host attributes
clixon-lib,yang
  - Moved all extended internal NETCONF attributes to the clicon-lib namespace
C-API:
  - wrapped most attribute creation into new fn xml_add_attr()

apps/snmp/snmp_main.c

@@ -525,7 +525,7 @@ main(int    argc,
      * used by the client, even though new TCP sessions are created for
      * each message sent to the backend.
      */
-    if (clicon_hello_req(h, &id) < 0)
+    if (clicon_hello_req(h, "cl:snmp", "localhost", &id) < 0)
         goto done;
     clicon_session_id_set(h, id);