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/vm/compiler/codegen/Optimizer.h b/vm/compiler/codegen/Optimizer.h
index dd8e788..43d98ed 100644
--- a/vm/compiler/codegen/Optimizer.h
+++ b/vm/compiler/codegen/Optimizer.h
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef _DALVIK_VM_COMPILER_OPTIMIZATION_H
-#define _DALVIK_VM_COMPILER_OPTIMIZATION_H
+#ifndef DALVIK_VM_COMPILER_OPTIMIZATION_H_
+#define DALVIK_VM_COMPILER_OPTIMIZATION_H_
 
 #include "Dalvik.h"
 
@@ -42,4 +42,4 @@
 
 void dvmCompilerApplyGlobalOptimizations(struct CompilationUnit *cUnit);
 
-#endif /* _DALVIK_VM_COMPILER_OPTIMIZATION_H */
+#endif  // DALVIK_VM_COMPILER_OPTIMIZATION_H_