doc: add some note for win32 module test

wfassoc/tests/concept.rs

@@ -318,12 +318,17 @@ fn test_verb() {
 
 #[test]
 fn test_cmd_line() {
+    // TODO: 
+    // Remove error tester dead_code attribute, 
+    // improve ok tester and add more error tests
+    // once we finish a complete CmdLine.
     fn ok_tester(s: &str) {
         let rv = CmdLine::from_str(s);
         assert!(rv.is_ok());
         // let rv = rv.unwrap();
         // assert_eq!(s, rv.full());
     }
+    #[allow(dead_code)]
     fn err_tester(s: &str) {
         let rv = CmdLine::from_str(s);
         assert!(rv.is_err());