Fix warnings_checker.dart handling of multitests

tests/language_strong/class_cycle2_test.dart

 // Copyright (c) 2011, 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.
 // Check fail because of cycles in super class relationship.
 
 class C extends B {}
 
 class A extends B {}
 
 class B
-  extends A // /// 01: compile-time error
-  extends A // /// 02: compile-time error
+  extends A // //# 01: compile-time error
+  extends A // //# 02: compile-time error
 {}
 
 main() {
-  new C(); // /// 01: continued
-  new List<C>(); // /// 02: continued
+  new C(); // //# 01: continued
+  new List<C>(); // //# 02: continued
 }