cleanup: get rid of the legacy #ifndef #define craziness

source/Irrlicht/COpenGLCoreCacheHandler.h

@@ -2,9 +2,7 @@
 // This file is part of the "Irrlicht Engine".
 // For conditions of distribution and use, see copyright notice in irrlicht.h
 
-#ifndef __C_OGLCORE_CACHE_HANDLER_H_INCLUDED__
-#define __C_OGLCORE_CACHE_HANDLER_H_INCLUDED__
-
+#pragma once
 
 #include "SMaterial.h"
 #include "ITexture.h"
@@ -639,5 +637,3 @@ protected:
 
 }
 }
-
-#endif