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/http_common.h b/http_common.h
index b2ffbc7..2c52445 100644
--- a/http_common.h
+++ b/http_common.h
@@ -5,8 +5,8 @@
 // This file contains general definitions used in implementing, testing and
 // emulating communication over HTTP.
 
-#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H__
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H__
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H_
 
 #include <stdlib.h>
 
@@ -55,4 +55,4 @@
 // Returns a standard HTTP Content-Type string.
 const char *GetHttpContentTypeString(HttpContentType type);
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H__
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H_