Migrate test block 30 + corelib portion of block 31 to Dart 2.0.

tests/corelib_2/unicode_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.
 
 import "package:expect/expect.dart";
 
 class UnicodeTest {
   static testMain() {
     var lowerStrasse = new String.fromCharCodes([115, 116, 114, 97, 223, 101]);
     Expect.equals("STRASSE", lowerStrasse.toUpperCase());
   }
 }
 
 main() {
   UnicodeTest.testMain();
 }