cosmetics: normalize include guards

use the recommended format [1] of:
<PROJECT>_<PATH>_<FILE>_H_

[1] https://google.github.io/styleguide/cppguide.html#The__define_Guard
"All header files should have #define guards to prevent multiple
inclusion. The format of the symbol name should be
<PROJECT>_<PATH>_<FILE>_H_."

Change-Id: I00a0595fc2a5fc736ab6ff3215727d6db05b10e1
diff --git a/aom_util/aom_thread.h b/aom_util/aom_thread.h
index fdb724d..f14c1ac 100644
--- a/aom_util/aom_thread.h
+++ b/aom_util/aom_thread.h
@@ -14,8 +14,8 @@
 // Original source:
 //  https://chromium.googlesource.com/webm/libwebp
 
-#ifndef AOM_THREAD_H_
-#define AOM_THREAD_H_
+#ifndef AOM_AOM_UTIL_AOM_THREAD_H_
+#define AOM_AOM_UTIL_AOM_THREAD_H_
 
 #include "config/aom_config.h"
 
@@ -427,4 +427,4 @@
 }  // extern "C"
 #endif
 
-#endif  // AOM_THREAD_H_
+#endif  // AOM_AOM_UTIL_AOM_THREAD_H_
diff --git a/aom_util/debug_util.h b/aom_util/debug_util.h
index 4096801..127a8b4 100644
--- a/aom_util/debug_util.h
+++ b/aom_util/debug_util.h
@@ -9,8 +9,8 @@
  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
  */
 
-#ifndef AOM_UTIL_DEBUG_UTIL_H_
-#define AOM_UTIL_DEBUG_UTIL_H_
+#ifndef AOM_AOM_UTIL_DEBUG_UTIL_H_
+#define AOM_AOM_UTIL_DEBUG_UTIL_H_
 
 #include "config/aom_config.h"
 
@@ -66,4 +66,4 @@
 }  // extern "C"
 #endif
 
-#endif  // AOM_UTIL_DEBUG_UTIL_H_
+#endif  // AOM_AOM_UTIL_DEBUG_UTIL_H_
diff --git a/aom_util/endian_inl.h b/aom_util/endian_inl.h
index 2d28221..f536ec5 100644
--- a/aom_util/endian_inl.h
+++ b/aom_util/endian_inl.h
@@ -11,8 +11,8 @@
 //
 // Endian related functions.
 
-#ifndef AOM_UTIL_ENDIAN_INL_H_
-#define AOM_UTIL_ENDIAN_INL_H_
+#ifndef AOM_AOM_UTIL_ENDIAN_INL_H_
+#define AOM_AOM_UTIL_ENDIAN_INL_H_
 
 #include <stdlib.h>
 
@@ -119,4 +119,4 @@
 #endif  // HAVE_BUILTIN_BSWAP64
 }
 
-#endif  // AOM_UTIL_ENDIAN_INL_H_
+#endif  // AOM_AOM_UTIL_ENDIAN_INL_H_