Add "deprecated" to the standard library.

pkg/meta/lib/meta.dart

 // 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.
 
 /**
  * Constants for use in metadata annotations such as
- * `@deprecated`, `@override`, and `@proxy`.
- * 
+ * `@proxy`.
+ *
+ * See also `@deprecated` and `@override` in the `dart:core` library.
+ *
  * Annotations provide semantic information
  * that tools can use to provide a better user experience.
  * For example, an IDE might not autocomplete
  * the name of a function that's been marked `@deprecated`,
  * or it might display the function's name differently.
  *
  * For information on installing and importing this library, see the
  * [meta package on pub.dartlang.org]
  * (http://pub.dartlang.org/packages/meta).
  * For examples of using annotations, see
  * [Metadata](https://www.dartlang.org/docs/dart-up-and-running/contents/ch02.html#ch02-metadata)
  * in the language tour.
  */
 library meta;
 
 /**
- * An annotation used to mark a class, field, getter, setter, method, top-level
- * variable, or top-level function as one that should no longer be used. Tools
- * can use this annotation to provide a warning on references to the marked
- * element.
- */
-const deprecated = const _Deprecated();
-
-class _Deprecated {
-  const _Deprecated();
-}
-
-/**
- * An annotation used to mark an instance member (method, field, getter or
- * setter) as overriding an inherited class member. Tools can use this
- * annotation to provide a warning if there is no overridden member.
- */
-const override = const _Override();
-
-class _Override {
-  const _Override();
-}
-
-/**
  * An annotation used to mark a class that should be considered to implement
  * every possible getter, setter and method. Tools can use this annotation to
  * suppress warnings when there is no explicit implementation of a referenced
  * member. Tools should provide a hint if this annotation is applied to a class
  * that does not implement or inherit an implementation of the method
  * [:noSuchMethod:] (other than the implementation in [Object]). Note that
  * classes are not affected by the use of this annotation on a supertype.
  */
 const proxy = const _Proxy();
 
 class _Proxy {
   const _Proxy();
-}
+}