[Perl/perl5] c69669: Consolidate and document all get_cvFOO() variants

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: c69669e6b6b6b3465e3305f37e45064632c82fac
      
https://github.com/Perl/perl5/commit/c69669e6b6b6b3465e3305f37e45064632c82fac
  Author: Karl Williamson <k...@cpan.org>
  Date:   2020-12-13 (Sun, 13 Dec 2020)

  Changed paths:
    M perl.c

  Log Message:
  -----------
  Consolidate and document all get_cvFOO() variants