Remove $FreeBSD$: one-line .c pattern

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

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

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Stop linking to libl by specifying we do not need yywrap

MFC after: 3 days

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.

Same as r316022 (Fix hexadecimal escape codes in jail.conf(5)),
but do it right this time.

Reported by: Kyle Evans <Kyle Evans>
MFC after: 3 days

Fix hexadecimal escape codes in jail.conf(5).

PR: 218154
Submitted by: Masahiro Konishi <mkonishi@sea.plala.or.jp>
MFC after: 3 days

Work around build breakages with GCC 4.2.

Reported by: tinderbox

Improve compatibility with recent flex from flex.sourceforge.net.

Add YY_NO_INPUT so clang doesn't complain about "input" not being used.

Update copyright dates and other whitespacey stuff.

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.