Manually enqueue compareTo, hashCode, ==, and toString in the Dart-to-Dart backend to avoid tree sh…

tests/corelib/regress_11099_test.dart

+// Copyright (c) 2013, 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.
+
+void main() {
+  var l = [new MyTest(1), new MyTest(5), new MyTest(3)];
+  l.sort();
+  if (l.toString() != "[d{1}, d{3}, d{5}]") throw 'Wrong result!';
+}
+
+class MyTest implements Comparable<MyTest> {
+  final int a;
+  MyTest(this.a);
+  int compareTo(MyTest b) => this.a - b.a;
+  String toString() => "d{$a}";
+}