pkgbase: put library links and symlinks in the -dev package

Some libraries (e.g. ncurses) install links to the main library for
backwards compatibilty. This change ensures that those links are in the
dev package since the files being linked to are in that package.

PR: 249143
MFC after: 1 week
Reviewed by: emaste, manu
Differential Revision: https://reviews.freebsd.org/D41841