Remove unused arguments from Graphics::Hitest()

The two arguments 'col' and 'col2', both the only integer arguments of
the function, do absolutely nothing. Remove those and update callers.

desktop_version/src/Graphics.h

@@ -132,7 +132,7 @@ public:
 
 	void render();
 
-	bool Hitest(SDL_Surface* surface1, point p1, int col, SDL_Surface* surface2, point p2, int col2);
+	bool Hitest(SDL_Surface* surface1, point p1, SDL_Surface* surface2, point p2);
 
 	void drawentities();