Provide SYS_statx for more target_arch/target_env

Fixes #1545

The syscall `statx` is provided by Linux Kernel, so it should be available on any `target_env`/`target_arch`, not only some arch on `gnu`.

Syscall ids are got from [this commit of musl](http://git.etalabs.net/cgit/musl/commit/?id=9864f60e929100e253fc813bd4105d6dd7652787), except for hexagon, which is got from Linux Kernel (`make O=build ARCH=hexagon headers`).

**Not tested yet**

Upgrade to musl 1.1.24 in CI

Required by #1577

Note that in musl 1.1.24, `struct sched_param` from `sched.h` has changed and some fields became reserved. So [these fields](https://github.com/rust-lang/libc/blob/13d4a5da2eafd82d3ebb2acb729d8b8c9148fb1f/src/unix/linux_like/mod.rs#L97) are outdated. I'm not sure if we should rename them, since they are in public API.

I simply skip `struct sched_param` from the test now.

Here's the diff between musl 1.1.23 and 1.1.24
```
diff --git a/include/sched.h b/include/sched.h
index 05d40b1e..7e470d3a 100644
--- a/include/sched.h
+++ b/include/sched.h
@@ -18,10 +18,12 @@ extern "C" {

 struct sched_param {
        int sched_priority;
-       int sched_ss_low_priority;
-       struct timespec sched_ss_repl_period;
-       struct timespec sched_ss_init_budget;
-       int sched_ss_max_repl;
+       int __reserved1;
+       struct {
+               time_t __reserved1;
+               long __reserved2;
+       } __reserved2[2];
+       int __reserved3;
 };
```

add pthread_getname_np for mac os

In macos's `pthread.h`

```c
/*SPI to set and get pthread name*/
__API_AVAILABLE(macos(10.6), ios(3.2))
int	pthread_getname_np(pthread_t,char*,size_t);

__API_AVAILABLE(macos(10.6), ios(3.2))
int	pthread_setname_np(const char*);
```

I believe `pthread_getname_np` is usable in macos after 10.6.

Signed-off-by: Yang Keao <keao.yang@yahoo.com>

Fix build.rs failing with a rustc built from a tarball

Fixes #1601

Fixes #1601

Implement utmpx to solaris/illumos

Closes #1535
I followed these references:

https://docs.oracle.com/cd/E23823_01/html/816-5168/getutxent-3c.html#REFMAN3Agetutxent-3c
https://github.com/illumos/illumos-gate/blob/4e0c5eff9af325c80994e9527b7cb8b3a1ffd1d4/usr/src/head/utmpx.h
https://github.com/illumos/illumos-gate/blob/4e0c5eff9af325c80994e9527b7cb8b3a1ffd1d4/usr/src/head/utmp.h

Nfnetfilter log

This adds the constants from linux/netfilter/nfnetlink.h and nfnetlink_log.h. These are the files I need for https://github.com/jbaublitz/neli/pull/48. After this gets in, I'd like to follow-up with the other nfnetlink_*.h files too, as I'd like to extend neli with further protocols in the future, but I want to do a smaller PR first to see if there are some things to tweak.

I've noticed similar netfilter constants are also in the android subfolder, therefore I'm adding them there too (I don't like the copy-pasting, but it seems the other ones are already copy-pasted). I assume the test will catch it if anything is different on that platform.

Add illumos 3socket flags

This adds missing flags for SOCKET(3SOCKET).

Add two missing pthread calls to the OpenBSD support.

These are shamelessly copied from the NetBSD support, whose prototypes in this regard are identical to OpenBSD's.

Add a few functions & POSIX error codes to Windows API

This change adds a few simple additional functions to the windows apis, as well as some additional error codes.

Tests and style pass, as per contributing guidelines.

Signed-off-by: Yang Keao <keao.yang@yahoo.com>

ci: switch mirrors to use our CDN

We recently added a CDN in front of our CI mirrors as it's faster and
cheaper for us. This switches libc's CI to use it instead of accessing
the underlying bucket directly.

r? @gnzlbg

Add struct ip_mreqn: ip multicast req with intf id

The ip_mreqn struct has an additional interface id parameter. This
allows programming IPv4 multicast groups using the interface id
alongside the src IPv4 address.
Linux has supported the ip_mreqn struct since Linux 2.2
ref: man ip.7

Add extended IFLA_ consts

Only Netlink interface link attributes up `IFLA_STATS` are currently available. This commit adds `IFLA_COST` to `IFLA_MAX_MTU`.

See https://github.com/torvalds/linux/blob/54ecb8f7/include/uapi/linux/if_link.h#L106

Thanks!

Add support for making functions `const`

PR https://github.com/rust-lang/rust/pull/64906 adds the ability to write `const extern fn` and `const unsafe extern fn`, which will allow manys functions in `libc` to become `const`.

This is particuarly useful for functions which correspond to C macros (e.g. `CMSG_SPACE`). In C, these macros are constant expressions, allowing them to be used when declaring arrays. However, since the corresponding `libc` functions are not `const`, writing equivalent Rust code is impossible. Users must either perform an unecessary heap allocation, or pull in `bindgen` to evaluate the macro for specific values (e.g. `CMSG_SPACE(1)`).

However, the syntax `const extern fn` is not currently parsed by rust. To allow libc to use this without breaking backwards compatibility (i.e. bumping the minimum Rust version), I've taken the following approach:

1. A new off-by-default feature `extern-const-fn` is added to `libc`.
2. The internal `f!` macro has two versions, selected at compile-time by a `cfg_if`. When `extern-const-fn` is enabled, the declared `f!` macro passes through the `const` keyword from the macro user to the final definition (`pub const unsafe extern fn foo`. When  `extern-const-fn` is disabled, the `const` keyword passed by the macro user is discarded, resulting in a plain `pub extern const fn` being declared.

Unfortunately, I couldn't manage to get `macro_rules` to accept a normal `const` token in the proper place (after `pub`). I had to resort to placing it in curly brackets:

```rust
pub {const} fn foo(val: u8) -> i8 {
}
```

The `f!` macro then translates this to a function definition with `const` in the proper position.

I'd appreciate it if someone who's more familiar with `macro_rules!` could see if I missed a way to get the desired syntax.

add shm support for NetBSD and OpenBSD

initial work from @landryb for OpenBSD, various fixes and NetBSD support from me.

Fixes #1585

shm support is need for firefox building (for slice-deque)

cc @jakllsch @ryoon for NetBSD

Minor Readme update

Deprecate vfork

The compiler may generate incorrect code for `vfork` and `setjmp` because they are missing the `#[returns_twice]` attribute which is currently unstable ([tracking issue](https://github.com/rust-lang/rust/issues/58314)). Since `vfork` is impossible to use safely, I propose deprecating it until `#[returns_twice]` is stable.

Disable broken targets

Only Netlink interface link attributes up IFLA_STATS are currently
available. This commit adds IFLA_COST to IFLA_PROTO_DOWN.

See https://github.com/torvalds/linux/blob/54ecb8f7/include/uapi/linux/if_link.h#L106

initial work from @landryb for OpenBSD, various fixes and NetBSD support from me.

Fixes #1585

Co-Authored-By: gnzlbg <gnzlbg@users.noreply.github.com>

First batch for #1562

Add a new feature to enable this, since `const extern fn`
support is unstable