Modal window - deletion instead of destroy

Replacing signal on_windowHelp_destroy with on_windowHelp_delete_event

+        # If you return FALSE in the "delete_event" signal handler,
+        # GTK will emit the "destroy" signal. Returning TRUE means
+        # you don't want the window to be destroyed.
+        # This is useful for popping up 'are you sure you want to
quit?'
+        # type dialogs.