Before, we had:

  site_perl :           lib/perl5/site_perl/5.18
  site_perl/perl_arch : lib/perl5/site_perl/5.18/mach
  perl_man3 :           lib/perl5/5.18/man/man3

Now we have:

  site_perl : lib/perl5/site_perl
  site_arch : lib/perl5/site_perl/mach/5.18
  perl_man3 : lib/perl5/site_perl/man/man3

Modules without any .so will be installed at the same place regardless of the
Perl version, minimizing the upgrade when the major Perl version is changed.
It uses a version dependent directory for modules with compiled bits.

As PERL_ARCH is no longer needed in plists, it has been removed from
PLIST_SUB.

The USE_PERL5=fixpacklist keyword is removed, the .packlist file is now
always removed, as is perllocal.pod.

The old site_perl and site_perl/arch directories have been kept in the
default Perl @INC for all Perl ports, and will be phased out as these old
Perl versions expire.

PR:		194969
Differential Revision:	https://reviews.freebsd.org/D1019
Exp-run by:	antoine
Reviewed by:	perl@
Approved by:	portmgr

- Cleanup PLIST