Update copyright notices in front_end package.

pkg/front_end/lib/src/scanner/errors.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2016, 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:analyzer/error/error.dart'
     show errorCodeValues, errorCodeByUniqueName;
 
 /**
  * An error code associated with an [AnalysisError].
  *
  * Generally, we want to provide messages that consist of three sentences. From
@@ skipping 338 matching lines @@
    */
   const ScannerErrorCode(String name, String message, [String correction])
       : super(name, message, correction);
 
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.ERROR;
 
   @override
   ErrorType get type => ErrorType.SYNTACTIC_ERROR;
 }