This enables us to require module versions, and to fall back to a
bundled version if the system version is too low.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6682)

Instead of having perl modules under test/testlib, util and util/perl,
consolidate them all to be inside util/perl.
Reviewed-by: NAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4069)

Reviewed-by: NRichard Levitte <levitte@openssl.org>

For our own convenience, we need a mechanism to be able to fall back
on bundled Perl modules.  It's a minimal package that's called like
this:

    use with_fallback qw(Module1 Module2 ...);

For each module, it will try to require them from the system
installation, and failing that, it will temporarly add external/perl
and try to require transfer::{ModuleName}.  It requires that each
bundled Perl modules is accompanied by a small transfer module
(external/perl/transfer/ModuleName.pm in our example) that knows
exactly what to load.
Reviewed-by: NRich Salz <rsalz@openssl.org>