handle "About..." menupick on OS X

[Kurt Kaufman]

Thanks for your suggestion, Malte.  I think that the biggest problem 
here is going to be that I have carefully laid out all of my objects in 
the stack window....if a portion is now to be covered by a menubar and 
subsequently hidden, then I have to rearrange everything!  Is this 
really the way it must work?  If so, it would be good practice to set up 
stacks intended for Mac distribution with a default menubar at the 
outset.  This should be mentioned in the docs (if it isn't).
Even better would be for the stack to be extended on TOP, so that no 
visible area would be hidden.
Again, if I'm missing something here, please set me straight!

-Kurt