Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

posix_spawn: If an error is detected in the child process, reap the zombie.

Formerly, in this case an error was returned but the pid was also returned
to the application, requiring the application to use unspecified behaviour
(the returned pid in error situations) to avoid zombies.

Now, reap the zombie and do not return the pid.

MFC after: 2 weeks

Fix whitespace inconsistencies in libc in files copyrighted by me.

posix_spawn(): Do not fail when trying to close an fd that is not open.

As noted in Austin Group issue #370 (an interpretation has been issued),
failing posix_spawn() because an fd specified with
posix_spawn_file_actions_addclose() is not open is unnecessarily harsh, and
there are existing implementations that do not fail posix_spawn() for this
reason.

Reviewed by: ed
MFC after: 10 days

Fix a typo.

Approved by: kib (mentor)

Turn execvpe() into an internal libc routine.

Adding exevpe() has caused some ports to break. Even though execvpe() is
a useful routine, it does not conform to any standards.

This patch is a little bit different from the patch sent to the mailing
list. I forgot to remove execvpe from the Symbol.map (which does not
seem to miscompile libc, though).

Reviewed by: davidxu
Approved by: philip

Process spawn attributes in POSIX document order.

Style fix.

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