Converge some changes from installperl into installman. I have a

Converge some changes from installperl into installman. I have a
suspicion that installman is only run on *nix and OS/2, not Win32 or
VMS. Specifically
sub unlink   - return scalar(@names) if $Is_VMS # from change 854
sub link     - change warn to die               # from change 4774
sub samepath - case insensitive name comparison # from change 311
(in the ansiperl branch, merged via the win32 branch)

p4raw-id: //depot/perl@33860