Revert "Add scoped helper to temporarily override current blitter"

This reverts commit ae701a3bd8.

src/blitter/factory.hpp

@@ -179,21 +179,6 @@ public:
 	 * Create an instance of this Blitter-class.
 	 */
 	virtual Blitter *CreateInstance() = 0;
-
-	/* Scoped temporary current blitter override */
-	struct TemporaryCurrentBlitterOverride {
-		Blitter *old_blitter;
-
-		TemporaryCurrentBlitterOverride(Blitter *new_blitter) : old_blitter(*GetActiveBlitter())
-		{
-			*GetActiveBlitter() = new_blitter;
-		}
-
-		~TemporaryCurrentBlitterOverride()
-		{
-			*GetActiveBlitter() = this->old_blitter;
-		}
-	};
 };
 
 extern std::string _ini_blitter;