Add appropriate LICENSE and Copyright message.

Summary:
Add appropriate LICENSE and Copyright message.

Test Plan:
make check

Reviewers:

CC:

Task ID: #

Blame Rev:

util/string_util.h

@@ -1,5 +1,8 @@
-// Copyright (c) 2013 Facebook.
-
+//  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+//  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.
+//
 #pragma once
 namespace rocksdb {