transitioning to stable libarchive

[rodent%NetBSD.org@localhost]

Hey,

We need to start transitioning from the legacy version of archivers/libarchive
we're maintaining to the new stable version of it. wip/nestopia wouldn't build
with the version we have now and we'll begin to see more of this with other
packages, likely. I created a very -wip (but working!) version in
wip/libarchive. wip/nestopia and devel/cmake builds with it, no problem. This
package is marked for update in doc/TODO, so perhaps it's something we could
sort this quarter.

Best regards,

rodent@