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 15:24:12 +0200
> 
> +      /* If downcasing changed an ASCII character into a non-ASCII
> +      character (this can happen in some locales, like the Turkish
> +      "I"), use the multibyte algorithm.  */
> +      if (SINGLE_BYTE_CHAR_P (ch) && !SINGLE_BYTE_CHAR_P (cased))
> +     return do_casify_multibyte_string (ctx, obj);
> +      SSET (obj, i, make_char_unibyte (cased));

Like I said elsewhere, I'd prefer to use ASCII rules in that case.
It's safer, and definitely less surprising.  Whoever wants Turkish
rules will need to submit multibyte strings, even for ASCII
characters.