Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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