[Perl/perl5] 7ebead: perlapi: Document SvPVXtrue

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 7ebead7d0c53181ea9cd65eff3102063798e60e7
      
https://github.com/Perl/perl5/commit/7ebead7d0c53181ea9cd65eff3102063798e60e7
  Author: Karl Williamson <k...@cpan.org>
  Date:   2022-04-25 (Mon, 25 Apr 2022)

  Changed paths:
    M sv.h

  Log Message:
  -----------
  perlapi: Document SvPVXtrue