Remove Expect from core library.

tests/language/strict_equal_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";
+
 
 main() {
   for (int i = 0; i < 6000; i++) {
     Expect.isFalse(test1(5));
     Expect.isTrue(test1(3));
 
     Expect.isTrue(test2(5));
     Expect.isFalse(test2(3));
 
     Expect.isTrue(test2r(5));
@@ skipping 112 matching lines @@
   if (identical(a, 0)) {
     Expect.isTrue(identical(0, a));
     Expect.isFalse(!identical(a, 0));
     Expect.isFalse(!identical(0, a));
   } else {
     Expect.isFalse(identical(0, a));
     Expect.isTrue(!identical(a, 0));
     Expect.isTrue(!identical(0, a));
   }
 }