[Perl/perl5] 4f3785: locale.c: toggling locales is a no-op if no locales

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 4f3785661c86751b74bdb1c94d0963829aa9a5b7
      
https://github.com/Perl/perl5/commit/4f3785661c86751b74bdb1c94d0963829aa9a5b7
  Author: Karl Williamson <k...@cpan.org>
  Date:   2024-01-02 (Tue, 02 Jan 2024)

  Changed paths:
    M locale.c

  Log Message:
  -----------
  locale.c: toggling locales is a no-op if no locales

When the only legal locale is C, toggling to another locale doesn't make
sense.  By #defining the macro that implements toggling this to do
nothing in this case, we can avoid some #ifdefs