posix_spawn(3): add POSIX_SPAWN_DISABLE_ASLR_NP

similar to Apple _POSIX_SPAWN_DISABLE_ASLR

Reviewed by: emaste, kevans
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D44195

Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

posix_spawn: add closefrom non-portable action

Namely posix_spawn_file_actions_addclosefrom_np, in the form it is
provided by glibc.

Reviewed by: kevans, ngie (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D33143

posix_spawn: add chdir-related non-portable actions

Namely posix_spawn_file_actions_addchdir_np and
posix_spawn_file_actions_addfchdir_np.

Reviewed by: kevans, ngie (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D33143

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.

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

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

- Import the HEAD csup code which is the basis for the cvsmode work.

Remove __restrict keywords from array arguments to make GCC's -std=c99 work.

When GCC is invoked with -std=c99, the following errors are displayed when
including <spawn.h>:

/usr/include/spawn.h:69: error: static or type qualifiers in abstract declarator
/usr/include/spawn.h:69: error: static or type qualifiers in abstract declarator
/usr/include/spawn.h:72: error: static or type qualifiers in abstract declarator
/usr/include/spawn.h:72: error: static or type qualifiers in abstract declarator

We'd better remove the __restrict keywords here. The same is also done
in <regex.h>.

Submitted by: Andrzej Tobola <ato iem pw edu pl>
Reviewed by: davidxu
Approved by: philip (mentor, implicit)

Change my email address to the one from the FreeBSD project.

Approved by: philip (mentor, implicit), davidxu

Add POSIX routines called posix_spawn() and posix_spawnp(), which
can be used as replacements for exec/fork in a lot of cases. This
change also added execvpe() which allows environment variable
PATH to be used for searching executable file, it is used for
implementing posix_spawnp().

PR: standards/122051