Correct file names for tests in tests/language.

tests/language/exception_in_increment_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.
 // Test throws exception in the middle of the increment operation, the setter
 // part of the instance field increment never completes.
 
 main() {
   var a = new A();
   a.field = new A();
   for (int i = 0; i < 4000; i++) {
     try {
       a.foo(i);
     } catch (e) {
       // Ignore.
     }
   }
 }
 
 class A {
   var field;
   foo(i) {
     field++;  // throw exception
   }
 }