The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.
Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix
libjail is pretty small, so it makes for a good proof of concept demonstrating
how a system library can be wrapped to create a loadable Lua module for flua.
* Introduce 3lua section for man pages
* Add libjail module
Reviewed by: kevans, manpages
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D26080