[Perl/perl5] 1d440e: Document gv_autoload4

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 1d440ec4903d5548d4d83f3e1d3547bbd528ae6f
      
https://github.com/Perl/perl5/commit/1d440ec4903d5548d4d83f3e1d3547bbd528ae6f
  Author: Karl Williamson <k...@cpan.org>
  Date:   2020-12-27 (Sun, 27 Dec 2020)

  Changed paths:
    M embed.fnc
    M gv.h

  Log Message:
  -----------
  Document gv_autoload4