Fix warnings_checker.dart handling of multitests

tests/language_strong/function_type_alias5_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Dart test for illegally self referencing function type alias.
 
-typedef Handle Handle(String command); // /// 00: compile-time error
+typedef Handle Handle(String command); // //# 00: compile-time error
 
-typedef F(F x); // /// 01: compile-time error
+typedef F(F x); // //# 01: compile-time error
 
-typedef A(B x); // /// 02: compile-time error
-typedef B(A x); // /// 02: continued
+typedef A(B x); // //# 02: compile-time error
+typedef B(A x); // //# 02: continued
 
 main() {
-  Handle h; // /// 00: continued
-  F f; // /// 01: continued
-  A f; // /// 02: continued
+  Handle h; // //# 00: continued
+  F f; // //# 01: continued
+  A f; // //# 02: continued
 }