Man pages for O_CLOFORK implementation

These are Ricardo Branco's man page updates for affected functions
using O_CLOFORK (and associated variants) for NetBSD (with
a few minor changes and additions by me).

libc: Expose pipe2 and dup3 to POSIX.2024 applications

branches: 1.32.8;
Refine the documentation

Sort includes.
Correct the historical note, pipe first appeared in AT&T UNIX v3.
Document ENOMEM.

Add pipe2 to the NAME section

pipe2 requires fcntl.h for its flags; PR 48614 from Steffen Daode Nurpmeso.
Also fix the wording for EINVAL as suggested by Robert Elz.

For pipe2(2), EINVAL won't be returned if the flag is O_NOSIGPIPE.

branches: 1.28.6;
As discussed in tech-kern, provide the means to prevent delivery of SIGPIPE
on EPIPE for all file descriptor types:

- provide O_NOSIGPIPE for open,kqueue1,pipe2,dup3,fcntl(F_{G,S}ETFL) [NetBSD]
- provide SOCK_NOSIGPIPE for socket,socketpair [NetBSD]
- provide SO_NOSIGPIPE for {g,s}seckopt [NetBSD/FreeBSD/MacOSX]
- provide F_{G,S}ETNOSIGPIPE for fcntl [MacOSX]

branches: 1.27.2;
Consistently mark up defined values with Dv.

mention EINVAL.

Small markup edit.

Various minor improvements.

* Arrange for interfaces that create new file descriptors to be able to
set close-on-exec on creation (http://udrepper.livejournal.com/20407.html).

- Add F_DUPFD_CLOEXEC to fcntl(2).
- Add MSG_CMSG_CLOEXEC to recvmsg(2) for unix file descriptor passing.
- Add dup3(2) syscall with a flags argument for O_CLOEXEC, O_NONBLOCK.
- Add pipe2(2) syscall with a flags argument for O_CLOEXEC, O_NONBLOCK.
- Add flags SOCK_CLOEXEC, SOCK_NONBLOCK to the socket type parameter
for socket(2) and socketpair(2).
- Add new paccept(2) syscall that takes an additional sigset_t to alter
the sigmask temporarily and a flags argument to set SOCK_CLOEXEC,
SOCK_NONBLOCK.
- Add new mode character 'e' to fopen(3) and popen(3) to open pipes
and file descriptors for close on exec.
- Add new kqueue1(2) syscall with a new flags argument to open the
kqueue file descriptor with O_CLOEXEC, O_NONBLOCK.

* Fix the system calls that take socklen_t arguments to actually do so.

* Don't include userland header files (signal.h) from system header files
(rump_syscallargs.h).

* Bump libc version for the new syscalls.

\- is a minus, not -.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22280, verified by myself.

Use
.In header.h
instead of
.Fd #include \*[Lt]header.h\*[Gt]
Much easier to read and write, and supported by groff for ages.
Okayed by ross.

Merge the nathanw_sa branch.

New sentence, new line. From Robert Elz.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

Grammar nit from 1.14.
Dd from 1.5.

Boring whitespace or punctuation fixes.

Clarify that you may get a signal instead of EFAULT.

Sort sections, sort SEE ALSO, punctuation and miscellanous fixes.

Boring whitespace fixes.

branches: 1.11.6;
Add a LIBRARY section to system call manual pages. While it's clear that the
libraries contain stubs only (with minor exceptions a la pipe(2)), the purpose
of this section is to provide linkage information.

branches: 1.10.6;
Last of the .Os cleanups. .Os is defined in the tmac.doc-common file,
so we shouldn't override it with versions in the manpages. Wheee!

"int filedes[2]" is more correct than "int *filedes" in synopsis.

Add missing `STANDARDS' compliance statements. As we #define _POSIX_VERSION
to 199009L, bump existing statements to 1003.1-1990.

Update standards conformance.

merge with lite, keeping most local changes. clean up Ids

pipe(2) is no longer implemented using socketpair(2).

branches: 1.4.2;
Use "Er" for argument to -width in the lists in the ERROR sections --- so
the formatting is consistant.

Clean up manpages:
Use .Fn rather than .Nm macro in HISTORY and STANDARDS sections.
Use .At and .St macros instead of spelling out "Version 6 UNIX",
"IEEE 1003.1-1988 (POSIX)", etc.

Add RCS indentifiers.

branches: 1.1.1;
Initial revision