Preparations for signed binary pkgs in netbsd-9

[Martin Husemann <martin%duskware.de@localhost>]

Hey folks,

last time I tried to find out why we do not have signed NetBSD binary
pkgs, I understood it was related to some issues with netbsd-7 and the
pkg tools used there.

Now that we will phase out netbsd-7 after the 9.0 release, it might be
a good time to think about pub key / certificate (or whatever is involved)
distribution with the 9.0 release.

So: what changes will the base system distribution need, and where do
we get the pub key to distribute with it (if such a thing exists),
and/or what changes does sysinst need to properly support it?

TIA,

Martin