Replace all include guard ifdefs with "#pragma once"

Source/Core/VideoBackends/Software/TextureSampler.h

@@ -2,9 +2,7 @@
 // Licensed under GPLv2
 // Refer to the license.txt file included.
 
-#ifndef _TEXTURESAMPLER_H_
-#define _TEXTURESAMPLER_H_
-
+#pragma once
 
 #include "Common.h"
 
@@ -16,6 +14,3 @@ namespace TextureSampler
 
 	enum { RED_SMP, GRN_SMP, BLU_SMP, ALP_SMP };
 }
-
-
-#endif