virtual/perl-*: Extend applicable stable keywords from dev-lang/perl

virtual/perl-*: Extend applicable stable keywords from dev-lang/perl

virtuals are by design an extension of Perl itself, so it rarely
makes sense for a virtual not to have a given keyword when Perl
has one.

Similarly, stabilization for Perl Itself should be communicated
out to all its virtuals.

However, in the past, the lack of keywords for certain arches has
resulted in those arches silently failing to stabilize these
virtuals, and the hope is this will make that problem go away.

Package-Manager: portage-2.3.3