build dom_tree_to_list_kvp_value more efficiently

seems to be unused however

libgnucash/backend/xml/sixtp-dom-parsers.cpp

@@ -321,10 +321,12 @@ dom_tree_to_list_kvp_value (xmlNodePtr node)
         new_val = dom_tree_to_kvp_value (mark);
         if (new_val)
         {
-            list = g_list_append (list, (gpointer)new_val);
+            list = g_list_prepend (list, (gpointer)new_val);
         }
     }
 
+    list = g_list_reverse (list);
+
     ret = new KvpValue {list};
 
     return ret;