Change: Use power-of-2 scaling for some dimensions in GUI.

These are related to drawing sprites that are normally drawn on the
landscape, and should therefore still follow power-of-2 scaling to fit
correctly.

src/zoom_func.h

@@ -99,6 +99,16 @@ static inline ZoomLevel UnScaleZoomGUI(ZoomLevel value)
 	return std::clamp(ZoomLevel(value - (ZOOM_LVL_GUI - ZOOM_LVL_OUT_4X)), ZOOM_LVL_MIN, ZOOM_LVL_MAX);
 }
 
+/**
+ * Scale traditional pixel dimensions to GUI zoom level, for drawing sprites.
+ * @param value Pixel amount at #ZOOM_LVL_BASE (traditional "normal" interface size).
+ * @return Pixel amount at #ZOOM_LVL_GUI (current interface size).
+ */
+static inline int ScaleSpriteTrad(int value)
+{
+	return UnScaleGUI(value * ZOOM_LVL_BASE);
+}
+
 /**
  * Scale traditional pixel dimensions to GUI zoom level.
  * @param value Pixel amount at #ZOOM_LVL_BASE (traditional "normal" interface size).