#1668 Menu geometry info wrong if cascaded

If you post a menu directly with the post widget
command, or associate it with a menubutton and click on
that to post it, you can get info about its position
using the wm or winfo commands. However if you display
it by clicking on a cascade entry in another menu, this
information is wrong. The geometry comes up as 0x0+1+1
if it is displayed for the first time, or whatever it
was when it was last invoked directly or from a menubutton.

Tested on TclTk 8.4.2 with red hat linux 7.3
and 8.4.3, 8.4.6, and 8.5a1 with red hat linux 9

[Donal K. Fellows]

Logged In: YES
user_id=79902

FWIW, the problem here stems from the fact that cascade
menus are actually (IIRC) using clones of the menu, and not
the menu itself. Usually the difference between a menu and
its clones is concealed, but this is obviously a spot where
it is not hidden.