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

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

MFC 249567: mdoc: remove superfluous paragraph macro.

MFC r249566,r249644: EINTR in POSIX sem_*.

Document that sem_wait() can fail with [EINTR].

Programs often do not expect an [EINTR] return from sem_wait() and POSIX
only allows it if the signal was installed without SA_RESTART. The timeout
in sem_timedwait() is absolute so it can be restarted normally.

The old POSIX semaphore implementation did this correctly, unlike the new
umtx one.

Specific to 9-stable: UMTX_ABSTIME does not exist and therefore
sem_timedwait() is erroneously not restarted after a SA_RESTART signal
handler.

It may be desirable to avoid [EINTR] completely, which matches the pthread
functions and is explicitly permitted by POSIX. However, the kernel must
return [EINTR] at least for signals with SA_RESTART clear, otherwise pthread
cancellation will not abort a semaphore wait. In this commit, only restore
the 8.x behaviour which is also permitted by POSIX, as far as possible with
the ABI in 9-stable.

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

Approved by: re (implicit)

Add missing section number.

In file sem_timewait.3, remove reference to SYSV semphore in SEE ALSO
section, sync it with sem_wait.3.

Cross-reference sem_getvalue(3) from several other semaphore-related
functions.

MFC after: 3 days

Markup tidying.

- libc/sys/sem.c was repocopied to libc/gen/sem.c.
- sem_*(3) manpages were repocopied from libc_r.

Reviewed by: deischen
Repocopy by: markm

The .Fn function. Use .Xr where appropriate.

Cross reference sem(4) so users know which kernel options are required
to use these semaphore functions.

mdoc(7) police: Use the new .In macro for #include statements.

Use ``.Rv -std'' wherever possible.

Submitted by: yar

Spell "FreeBSD" with "F" and "BSD" in uppercase.

Remove whitespace at EOL.

Use ``.St -p1003.1-96''.

Change my email address in the copyright notices for the sake of consistency
(jasone@canonware.com --> jasone@freebsd.org).

Introduce .Lb macro to libc_r manpages.

Add man pages for the sem_*() functions.

Approved by: jkh