(svn r23314) -Add: Add settings to restrict viewport zoom levels.

src/settings.cpp

@@ -894,6 +894,13 @@ static bool InvalidateVehTimetableWindow(int32 p1)
 	return true;
 }
 
+static bool ZoomMinMaxChanged(int32 p1)
+{
+	extern void ConstrainAllViewportsZoom();
+	ConstrainAllViewportsZoom();
+	return true;
+}
+
 /**
  * Update any possible saveload window and delete any newgrf dialogue as
  * its widget parts might change. Reinit all windows as it allows access to the