Add copyright notice to .pm file

Change-Id: Iff58d5746af20431f9e91f030da47b7beabbd76d

build/make/thumb.pm

 #!/usr/bin/env perl
 ##
-##  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+## Copyright (c) 2016, Alliance for Open Media. All rights reserved
 ##
-##  Use of this source code is governed by a BSD-style license
-##  that can be found in the LICENSE file in the root of the source
-##  tree. An additional intellectual property rights grant can be found
-##  in the file PATENTS.  All contributing project authors may
-##  be found in the AUTHORS file in the root of the source tree.
+## This source code is subject to the terms of the BSD 2 Clause License and
+## the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+## was not distributed with this source code in the LICENSE file, you can
+## obtain it at www.aomedia.org/license/software. If the Alliance for Open
+## Media Patent License 1.0 was not distributed with this source code in the
+## PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 ##
 
 package thumb;