Removes dartc reliance on its own libraries, now can be targeted at any implementation's libraries

compiler/lib/implementation/bool.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.
-
-// Adds Dart-methods to the prototype of the JS Boolean function.
-// TODO(floitsch): the following comment needs to be updated once we compile
-// boolean checks with '=== true'.
-// WARNING: 'this' inside this class is always treated as 'true'.
-// That is if (this) ... will always pick the 'then' branch.
-// The reason is that, once compiled to JS, 'this' is represented by a
-// JS Boolean object. However "if (new Boolean(false)) .." picks the then
-// branch.
-class BoolImplementation implements bool native "Boolean" {
-  bool operator ==(other) native;
-
-  // TODO(floitsch): we should intercept toString for primitives, to avoid
-  // creating a wrapper object.
-  String toString() native;
-
-  BoolImplementation toBool() native;
-
-  get dynamic() { return toBool(); }
-}