Add copyright header to generated analyzer files.

pkg/analyzer/lib/src/generated/ast.dart

+// Copyright (c) 2014, 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 code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.ast;
 
 import 'dart:collection';
 import 'java_core.dart';
 import 'java_engine.dart';
 import 'source.dart' show LineInfo;
 import 'scanner.dart';
@@ skipping 16360 matching lines @@
   }
   void operator[]=(int index, E node) {
     if (index < 0 || index >= _elements.length) {
       throw new RangeError("Index: ${index}, Size: ${_elements.length}");
     }
     owner.becomeParentOf(node);
     _elements[index] = node;
   }
   int get length => _elements.length;
 }