Update language tests to new optional parameter syntax and semantics.

tests/language/parameter_initializer_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.
 
 class ParameterInitializerTest {
 
   static testMain() {
     var obj = new Foo.untyped(1);
     Expect.equals(1, obj.x);
 
     obj = new Foo.supertype(9);
     Expect.equals(9, obj.x);
 
     obj = new Foo.subtype(7);
     Expect.equals(7, obj.x);
 
-    obj = new Foo.optional(x: 111);
+    obj = new Foo.optional(111);
     Expect.equals(111, obj.x);
 
     obj = new Foo.optional();
     Expect.equals(5, obj.x);
 
     obj = new Foo(1);
     Expect.equals(2, obj.x);
 
     obj = new SubFoo(42);
     Expect.equals(1, obj.x);
@@ skipping 46 matching lines @@
     Expect.equals(x_, 1);
 
     // There is no way to get to the field in Foo.
     Expect.equals(super.x, 1);
   }
 }
 
 main() {
   ParameterInitializerTest.testMain();
 }