Added reservation for the built-in function names;

lib/rpc.c

@@ -102,6 +102,8 @@ int sxmp_rpclist_add_function(usrtc_t *tree, int type, const char *fu_name,
   sxl_rpclist_t *rlist;
   sxl_rpc_t *rentry = NULL;
 
+  if(*fu_name == '!') return EINVAL; /* reserve such names for ither purposes */
+
   node = usrtc_lookup(tree, &type);
   if(!node) return ENOENT;
   else tlist = (rpc_typed_list_t *)usrtc_node_getdata(node);