When enabled (current default) link with --undefined-version to allow
symbol maps to contain symbols not defined by libraries. When disabled,
link with --no-undefined-version to disallow these bugs.
WITHOUT_UNDEFINED_VERSION is currently broken. Once it is fixed it
should be made the default and this option should likely be removed.
Reviewed by: dim, emaste
Differential Revision: https://reviews.freebsd.org/D44169
