Update the meta package to use the new pub format.

pkg/meta/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.
-
-/**
- * This library contains the definitions of annotations that provide additional
- * semantic information about the program being annotated. These annotations are
- * intended to be used by tools to provide a better user experience.
- */
-#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();
-}