[Perl/perl5] e53889: export the win32 symlink related symbols

[Tony Cook via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: e5388933b79bba4c658121614da1fb0ed1f55416
      
https://github.com/Perl/perl5/commit/e5388933b79bba4c658121614da1fb0ed1f55416
  Author: Tony Cook <t...@develop-help.com>
  Date:   2021-01-05 (Tue, 05 Jan 2021)

  Changed paths:
    M makedef.pl

  Log Message:
  -----------
  export the win32 symlink related symbols

I couldn't make the build fail due to these missing exports
while I was developing the win32 symlink() support, but I did
have it fail while testing an unrelated change, and reproduced it,
so export them.