[plt-scheme] Usability: Macro stepper

Hi,

These issues are quite minor, but I believe it is useful to care for
the details so even beginners can say "well, at first it was
intimidating, but it's all logical and well thought". My suggestions
this time are all pretty small changes.

So, this time I looked at the macro stepper. The menus seem to be
inconsistend with their use of separators: the "File" menu uses a
seperator above the "Quit", as does the "Edit" menu. No other menu in
DrScheme does this.

The "Edit" menu uses double-separators, which no other DrScheme menu
does, not even other menus in the stepper.

Besides this, the "Help" menu is empty, when I click on it I get an
empty menu which is a bit like "Here you can find help... oh, right,
there's no help for this" ;)

Anyway, thanks for DrScheme - while I didn't like it initially, it gets
better and better the more I use it.

regards,
Marek