[GUI] Proposal for MacOS MenuBar

[Wolfgang Thaller]

>    I propose simple scheme for portable for menus
> based on two simple ideas:
>  [...]  I hope that this can be suitable for MacOS.

Basically, that should work.

Mac OS provides another menu-related challenge: some menus
are created automatically or semi-automatically by the system.
Most important is the Quit menu item, which is found in the 
(system-generated)
Application menu, to the left of the File menu. Some other menu
items (About, Preferences) are supposed to be added to this
Application menu.

Cheers,

Wolfgang