Fixes #1775

https://reviews.freebsd.org/rS357382

Plus, add new constants for sysctls that give names to existing magic numbers.

https://reviews.freebsd.org/rS350749
https://reviews.freebsd.org/rS352486

Wide chars are unsigned when normal chars are

sys/stat.h is a machine-independent header, but it has ifdefs for i386.
The version that was called x86_64.rs should be used on powerpc64 too,
but I don't have a machine to test that on.

I just got 'libxul.so: Undefined symbol "mq_close"' when rebuilding Firefox..
How did no one catch this before??

This is correct for both FreeBSD and DragonFly:
https://github.com/freebsd/freebsd/blob/master/lib/librt/Symbol.map
https://github.com/DragonFlyBSD/DragonFlyBSD/blob/e7ab884bd49753f8884eb597d10d6569a08fa0df/lib/librt/mq.c
https://github.com/DragonFlyBSD/DragonFlyBSD/blob/e7ab884bd49753f8884eb597d10d6569a08fa0df/lib/librt/aio.c

This patchs adds missing flag values for getnameinfo()
on FreeBSD, the following flags have been added from
the FreeBSD tree.

 /*
  * Flag values for getnameinfo()
  */
 #define	NI_NOFQDN	0x00000001
 #define	NI_NUMERICHOST	0x00000002
 #define	NI_NAMEREQD	0x00000004
 #define	NI_NUMERICSERV	0x00000008
 #define	NI_DGRAM	0x00000010
 #define	NI_NUMERICSCOPE	0x00000020

Signed-off-by: Valdemar Erk <valdemar@erk.io>

Reorganized some constants as well so they're grouped a bit better.

Like on NetBSD, but without a pid field in the struct.

It is present on both FreeBSD and DragonFly

Headers I used:

Oh, for reference, here are the headers I used while working on this:

- musl: https://git.musl-libc.org/cgit/musl/tree/include/regex.h?id=8327ae0cb23b799bc55a45e0d4bd95f5a2b1cdf1
- glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=posix/regex.h;h=87cce7f5cb8cc3b678467329b479bd511e250e61;hb=HEAD
- macOS: https://opensource.apple.com/source/Libc/Libc-997.90.3/include/regex.h.auto.html
- FreeBSD: https://github.com/freebsd/freebsd/blob/8103b0ddb041617b7cd161528f0ff93ff32970a2/include/regex.h
- NetBSD: https://github.com/NetBSD/src/blob/61c8f6fbb7e38b20e862d5cb3ed2203312963283/include/regex.h

memmem is a non-standard extension, first added in GNU libc and later
ported to other systems. Support for it is non-uniform, thus it was only
added to platforms that seem to support it.

This triggers a warning on a recent nightly, which in turn breaks CI due to
`#![deny(warnings)]` in libc-test/build.rs

It's *msg_prio* in both manpages and posix.

This adds libc-test support for Freebsd10 and a CI build job that tests
FreeBSD10 with LIBC_CI only.

This value can vary at runtime.  Applications should instead use
sysconf(3) with _SC_AIO_LISTIO_MAX.

This constant is not stable across OS versions, so it cannot be used in
any backwards- or forwards- compatible way.  It's typically used to size
arrays in the kernel and in debugging utilities that are closely tied to
the OS version.  Since libc is ignorant about OS versions, we shouldn't
even be defining it.

This adds a few missing constants from DragonflyBSD `utmpx.h`.

Ref: http://gitweb.dragonflybsd.org/dragonfly.git/blob/HEAD:/include/utmpx.h

This adds a few missing constants from FreeBSD `utmpx.h`.

Ref: https://github.com/freebsd/freebsd/blob/a1d2b5187332a366a897689c5fb41d38d7e1b0d8/include/utmpx.h