Fix warnings_checker.dart handling of multitests

tests/language_strong/malformed_bound_test.dart

 // Copyright (c) 2014, 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.
 
 // Test that a malformed type variable bound is treated as dynamic.
 
 class C<T
-  extends Malformed /// 01: static type warning, runtime error
+  extends Malformed //# 01: static type warning, runtime error
 > {
-  f(T t) => t.foo; /// 01: continued
+  f(T t) => t.foo; //# 01: continued
 }
 
 main() {
   new C<int>()
-    .f(1) /// 01: continued
+    .f(1) //# 01: continued
   ;
 }