The pr #1870 introduced safe_f! macro, which made some functions like
WIFEXITED and WEXITSTATUS const and safe on linux_like platform only,
which causes inconsistency when trying to use those functions in crates
compiled across multiple platforms, as using unsafe on those functions
will generate unused_unsafe warning on linux platforms and lack of
unsafe block will fail compilation on non-linux platforms.

To avoid the inconsistency, this commit applies the same macro for all
the same functions on other platforms too.

Add getitimer and setitimer for macOS

These constant can be used to determine the maximum number of iovecs can
be passed to functions like readv/writev.

Linux like uses UIO_MAXIOV, while the BSD family uses IOV_MAX.

Expose __errno_location() (introduced in DragonFlyBSD 5.8), which
returns the current thread's errno value. This is similar to Linux
and avoids having a separate module that defines both errno (which
depends on the thread_local feature) and an __error() function.

Previously clock_getcpuclockid was enabled only on linux, with this
change it is enabled on all linux_like and freebsdlike.

On Linux, siginfo_t cannot expose these fields directly due to
https://github.com/rust-lang/libc/issues/716 , so expose them as
functions, just like si_addr and si_value.

In order to get alignment correct on both 32-bit and 64-bit
architectures, define an sifields union that includes a pointer field,
to ensure that it has the same alignment as a pointer.

Allows us to get a pthread id from a match thread id.
From pthread.h [1]:

```
__API_AVAILABLE(macos(10.5), ios(2.0))
_Nullable pthread_t pthread_from_mach_thread_np(mach_port_t);
```

[1] - https://opensource.apple.com/source/libpthread/libpthread-416.40.3/pthread/pthread.h.auto.html

It's been removed in FreeBSD 13 (svn r363622), and never had any
legitimate use outside of the base system anyway.

https://github.com/openbsd/src/blob/b66614995ab119f75167daaa7755b34001836821/sys/sys/wait.h#L52

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