[Perl/perl5] 952fa0: locale.c: Change macro name 'porcelain' => 'posix'

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 952fa04f7f2a5518f11f811d9ee21670671c1994
      
https://github.com/Perl/perl5/commit/952fa04f7f2a5518f11f811d9ee21670671c1994
  Author: Karl Williamson <k...@cpan.org>
  Date:   2022-09-10 (Sat, 10 Sep 2022)

  Changed paths:
    M locale.c

  Log Message:
  -----------
  locale.c: Change macro name 'porcelain' => 'posix'

When I wrote this I tought porcelain in git meant something different
than it does.  But what this macro does is to hide the non-POSIX vs
POSIX differences from its callers.