MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

usr.sbin: minor spelling fixes on comments.

No functional change.

Fix a ton of speelling errors

arc lint is helpful

Reviewed By: allanjude, wblock, #manpages, chris@bsdjunk.com
Differential Revision: https://reviews.freebsd.org/D3337

A new jail(8) with a configuration file, ultimately to replace the work
currently done by /etc/rc.d/jail.

MFC after: 3 months

Update copyright dates and other whitespacey stuff.

Change cfstrings from an STAILQ into a TAILQ to allow commands to be
traversed in reverse order.

Initial work on the new jail(8). There are more features to add, and some
cleaning up to do on existing features, but this is pretty much what the
final product will look like.