Remove references to GPLv2 license

License headers added to Makefiles were taken from `zstd/Makefile`.

examples/Makefile

@@ -1,26 +1,11 @@
-# ##########################################################################
-# ZSTD educational examples - Makefile
-# Copyright (C) Yann Collet 2016
+# ################################################################
+# Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+# All rights reserved.
 #
-# GPL v2 License
-#
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License along
-# with this program; if not, write to the Free Software Foundation, Inc.,
-# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
-#
-# You can contact the author at :
-#  - zstd homepage : http://www.zstd.net/
-# ##########################################################################
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree. An additional grant
+# of patent rights can be found in the PATENTS file in the same directory.
+# ################################################################
 
 # This Makefile presumes libzstd is installed, using `sudo make install`