Replace all include guard ifdefs with "#pragma once"

Source/Core/VideoCommon/VideoState.h

@@ -2,8 +2,7 @@
 // Licensed under GPLv2
 // Refer to the license.txt file included.
 
-#ifndef _VIDEOSTATE_H
-#define _VIDEOSTATE_H
+#pragma once
 
 #include "Common.h"
 #include "ChunkFile.h"
@@ -11,5 +10,3 @@
 void VideoCommon_DoState(PointerWrap &p);
 void VideoCommon_RunLoop(bool enable);
 void VideoCommon_Init();
-
-#endif // _VIDEOSTATE_H