Fix header guards to comply with Google Coding Style.

The Google Style Guide says that every header file should have a
define guard and the format of the symbol name should be
  <PROJECT>_<PATH>_<FILE>_H_

This patch does all the minor fixes to comply with this and includes
a header guard for the bzip.h file, which didn't have it.

Also, the Copyright notice is adjusted to the Chromium OS code,
replacing "Chromium Authors" by "Chromium OS Authors".

BUG=None
TEST=build passes.

Change-Id: I6575cc307c464d60a5cb2b132cf1e46acb6500b5
Reviewed-on: https://chromium-review.googlesource.com/190445
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
diff --git a/bzip.h b/bzip.h
index ca6e881..4f70d74 100644
--- a/bzip.h
+++ b/bzip.h
@@ -1,7 +1,10 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_BZIP_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_BZIP_H_
+
 #include <string>
 #include <vector>
 
@@ -14,3 +17,5 @@
 bool BzipDecompressString(const std::string& str, std::vector<char>* out);
 
 }  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_BZIP_H_