Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

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(cherry picked from commit fa9896e082a1)

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

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(cherry picked from commit d0b2dbfa0ecf)

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

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(cherry picked from commit b3e7694832e8)

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

(cherry picked from commit 4d846d260e2b9a3d4d0a701462568268cbfe7a5b)

- no blank before trailing delimiter
- whitespace at end of input line
- sections out of conventional order
- normalizing date format
- AUTHORS section without An macro

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.

Sponsored by:	Dell EMC Isilon

Off by default, build behaves normally.
WITH_META_MODE we get auto objdir creation, the ability to
start build from anywhere in the tree.

Still need to add real targets under targets/ to build packages.

Differential Revision:       D2796
Reviewed by: brooks imp