Clone stack invisibly

[Robert Brenstein]

>Just make the stack not visible before cloning it.
>
>Tested in the Script Editor installer... For a later release! ;)
>

I can confirm that this works. However, a word of caution: when a 
stack opens invisible, it does not get all of the normally expected 
"open" messages (behavior confirmed by Scott Raney so not considered 
as a bug so far).

Robert Brenstein