pipeline_exec() complete

+ TODO : simple_cmd_builtin()
+ libft small update

srcs/parsing/expansions/new_token_for_each_field.c

@@ -56,7 +56,7 @@ static t_token	*insert_tokens(t_token *t, t_token *insert_lst)
 
 	t->id = 0;
 	free(t->content);
-	t->content = NULL;
+	t->content = NULL; // TODO : free_null()
 	if (!insert_lst)
 		return (t);