bug#52874: 26.3; Be able to keep current menu-bar menus when minibuffer is used

[Drew Adams]

When the minibuffer is used the menu-bar automatically changes to
provide menus appropriate for using the minbuffer.  This is a good
thing.

However, there can be use cases for keeping the menu-bar as it was
before the minbuffer was entered.  This can be the case if the
minibuffer is used to access menu-bar menu items (using completion, for
instance).  In such contexts it can make sense for the command reading
from the minibuffer to be able to keep the menu-bar as it was, so users
can see what the menu names are.

This enhancement request is to provide that possibility in Lisp - for
example by binding a global variable.

In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor `Microsoft Corp.', version 10.0.19042
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''