Normalize the include guard style.

An leading underscore followed by a capital letter is a reserved
name space in C and C++.

This change also moves any #include directives within the include
guard in some of the compiler/codegen/arm header files.

Change-Id: I9715e2c5301699d31886e61d0fe6e29483555a2a
diff --git a/include/nativehelper/JNIHelp.h b/include/nativehelper/JNIHelp.h
index c45445c..aa98c2c 100644
--- a/include/nativehelper/JNIHelp.h
+++ b/include/nativehelper/JNIHelp.h
@@ -20,8 +20,8 @@
  * This file may be included by C or C++ code, which is trouble because jni.h
  * uses different typedefs for JNIEnv in each language.
  */
-#ifndef _NATIVEHELPER_JNIHELP_H
-#define _NATIVEHELPER_JNIHELP_H
+#ifndef NATIVEHELPER_JNIHELP_H_
+#define NATIVEHELPER_JNIHELP_H_
 
 #include "jni.h"
 #include "cutils/log.h"
@@ -189,4 +189,4 @@
     _rc; })
 #endif
 
-#endif /*_NATIVEHELPER_JNIHELP_H*/
+#endif  /* NATIVEHELPER_JNIHELP_H_ */