Remove $FreeBSD$: one-line sh pattern

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

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Move to using newvers -c instead of VARS_ONLY=1

Use newvers.sh -c to get the copyright, and newvers.sh -V RELDATE to
get the release date.

Differential Revision: https://reviews.freebsd.org/D19849

include: General further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified 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.

Stop building vers.c in include/ and only build the needed osreldate.h.

Because of how osreldate.h was being built with newvers.sh, which always
spat out a vers.c dependent on SVN or git, the meta mode build was
considering osreldate.h to depend on the current git or SVN index. This
would lead to entire tree rebuilds when modifying git's index. There's
no reason to be generating vers.c here so just skip it.

While here, in mk-osreldate.sh rename PARAM_H to proper PARAMFILE (which
newvers.sh already has a default for) and remove unneeded export.

Sponsored by: EMC / Isilon Storage Division

Misc fixes from projects/bmake

Differential Revision: D2748
Reviewed by: brooks imp

use mv -f to avoid questions

Set proper permissions on the generated osreldate.h file; a file readable
only by root can cause install problems, especially over nfs.

Submitted by: jilles@
Approved by: re (gjb)

Prevent the set -e from mk-osreldate.sh from propagating into newvers.sh.
This would cause detection of old versions of SVN to cause fatal errors
instead of being caught and handled, which would make the build fail if
the tree had been checked out with an older version of SVN (e.g. 1.6).

Discussed with: gjb
Approved by: re (marius)

Create a separate script to generate osreldate.h rather than sourcing
newvers.sh into a temporary subshell with inline make rules.

Using a separate script fixes a variety of problems, including establishing
the correct dependencies in the makefiles. It also eliminates a problem
with the way newvers.sh uses `realpath $0`, because $0 expands differently
within a script sourced into a rule in a makefile depending on the version
of make and of /bin/sh being used. The latter can cause build breakage in a
cross-build environment, and can also make it difficult to compile 10.0 on
older pre-10.0 systems.

PR: 160646 174422
Submitted by: Garrett Cooper <yaneurabeya@gmail.com>
Approved by: re (gjb)
MFC after: 2 weeks