test rename overhaul: step 8 - language tests

tests/language/default_class_implicit_constructor_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.
 
 // An interface with a default class with no declared constructor should 
 // use the implicit default constructor
 
 interface A default B {
   A();
 }
 
 class B implements A {
 }
 
 main() {
   var val = new A();
   Expect.equals(true, val is A);
   Expect.equals(true, val is B);
 }