jail: make sure jail.conf parse errors exit, and not crash.
Reported by: Mason Loring Bliss

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

jail: add ".include" directive to jail.conf

Jail config files can now include literal filenames and file globs.
They can not (yet) include files based on variables/parameters.

jail: Use re-entrant versions of lex & yacc, and lex's yylineno

jail: Allow nested jail definitions.

Make the jail.conf specification recursive, with jail definitions
allowed within a jail's parameter list, just as they are allowed
at the top level. Such inner jails are part of the outer jail's
hierarchy, as if they were specified with hierarchical names.

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

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

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.

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

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.