Move core and coreimpl from corelib/ to lib/core and lib/coreimpl.

corelib/src/implementation/print.dart

Index: corelib/src/implementation/print.dart
diff --git a/corelib/src/implementation/print.dart b/corelib/src/implementation/print.dart
deleted file mode 100644
index 51a83beb3d9e1dbd203c6cd473a4ae720d4dd837..0000000000000000000000000000000000000000
--- a/corelib/src/implementation/print.dart
+++ /dev/null
@@ -1,7 +0,0 @@
-// 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 PrintImplementation {
-  external static void print(Object obj);
-}