Prevent an infinite loop that occurred if player clicked on the
close window button and then tried to cancel out of that in the
dialog it brings up.
I don't know whether Qt interface on platforms other than OSX
need this but they're getting it. The choices are changed from
"Save" or "Cancel" to "Save and exit" or "Quit without saving".
Since save allows subsequent restore, not being able to cancel
out of the application shutdown should only be an inconvenience.
Unresolved issues:
I don't know whether there's any other way to bring up that dialog,
where Cancel might be a viable choice. If so, handling that might
be tricky. Quit should definitely be available as an alterative
to Save, but that type of dialog doesn't seem to allow more than
two choices.
Picking "nethack" from application menu and then "quit nethack"
from the resulting pull down menu results in executing nethack's
help command (the '?' menu) and then just resumes play.
addebf7090