[json] Update the internal JSON-GLib copy

There have been changes in JSON-GLib upstream to clean up the
data structures, and facilitate introspection.

We still not use the updated JsonParser with the (private) JsonScanner
code, since it's a fork of GLib's GScanner.

clutter/clutter-script.c

@@ -702,7 +702,7 @@ json_object_end (JsonParser *parser,
 
       val = json_node_new (JSON_NODE_VALUE);
       json_node_set_string (val, fake);
-      json_object_add_member (object, "id", val);
+      json_object_set_member (object, "id", val);
 
       g_free (fake);
     }