bug#45806: 26.3; `menu-bar-separator'

[Drew Adams]

This variable (defconst) doesn't seem to be documented anywhere.

It seems to be used for menus in general; it doesn't seem to be tied to
the menu-bar in any way.  And its only doc is the doc string, which says
only "Separator for menus."  Could it be renamed to remove any mention
of the menu-bar (keeping the old name as alias)?

How is it actually used?  Is it used only in (some?) toolkits?

It's a defconst (why?), so presumably you shouldn't change it.  But
changing it doesn't seem to have any effect anyway, in MS Windows.  If
this is hard-coded then why is it even needed?

In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor `Microsoft Corp.', version 10.0.18362
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''