bug#50752: 28.0.50; easy-menu-define lowers the menu-bar key

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: stefan@marxist.se,  shuguang79@qq.com,  50752@debbugs.gnu.org
> Date: Tue, 19 Oct 2021 14:45:23 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > You mean, you want to special-case Turkish (and a couple of similar)
> > locale?
> 
> Nope.  The loop can just check whether we get a multibyte result when
> downcasing unibyte (ASCII), and then defer to the multibyte version to
> do the computation.
> 
> This will basically only happen when using a Turkish (and a couple
> similar) locales, though, so the general performance impact will be
> approximately nil.

I'd actually prefer to ignore any locale-specific behavior that take
an ASCII character and downcases (or upcases) it to a non-ASCII one,
in the unibyte case.  IOW, if changing a case of an ASCII character
from a unibyte string produces a non-ASCII multibyte character,
disregard any locale-specific case-conversion and use US ASCII rules.
That at least has the chance of not adversely affecting anything,
whereas producing non-ASCII multibyte string instead is IMO much
worse.