Fix missing title screen in Growlanser & incorrect switch between buffered and non-buffered mode

This one is pretty simple and straightforward logic.

	if (viewport_width != 480 && viewport_height != 272) { 
		drawing_width = std::min(scissorX2, regionX2);
		drawing_height = std::min(scissorY2, regionY2);
	} else {
		drawing_width = viewport_width;
		drawing_height = viewport_height;
	}