Currently, libc supports and detects freebsd11 and freebsd13
Unknown versions, like freebsd13, is treated as freebsd11.
This patch solve the issues, detecting freebsd13 and treating it like
freebsd12.
Inverting the logic not(freebsd12) -> freebsd11 where possible

Add __errno_location on Redox, DragonFlyBSD, Haiku

Currently [`libstd`](https://github.com/rust-lang/rust/blob/909f5a049415a815b23502a5498de9a99bbf276b/src/libstd/sys/unix/os.rs#L29-L49) and the [`getrandom` crate](https://github.com/rust-random/getrandom/pull/54/files#diff-027a56068e2bf3d31dc4273ee6e07034R12) have to use external declarations in order to implement `errno_location` across all UNIX platforms. This change adds bindings for the remaining UNIX platforms, allowing everyone to just use normal `libc` bindings.

This also removes the need for a seperate [`errno-dragonfly`](https://crates.io/crates/errno-dragonfly) crate.

Links to the relevant header files:

- Redox: [`relibc`'s `bits/errno.h`](https://github.com/redox-os/relibc/blob/master/include/bits/errno.h) uses `__errno_location`
- Haiku: [`posix/errno.h`](https://github.com/luciang/haiku/blob/master/headers/posix/errno.h) uses `_errnop`
- DragonFlyBSD: [`sys/errno.h`](https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/errno.h) uses `__error` just like FreeBSD (which makes sense)
  - Note that the `__error` function is inlined. I don't think this causes a problem.

Support pthread_{set,get}name_np for linux with glibc

Add missing syscalls for aarch64-unknown-linux-musl

The list of syscalls from [rust-lang-aarch64-musl-syscalls](../blob/master/src/unix/notbsd/linux/musl/b64/aarch64.rs) misses some of the syscalls that are defined in [musl-libc-aarch64-syscalls](https://git.musl-libc.org/cgit/musl/tree/arch/aarch64/bits/syscall.h.in).
We need this so that we get rid of hardcoding them inside [our project](https://github.com/firecracker-microvm/firecracker/blob/master/vmm/src/default_syscalls/filters.rs#L16

).

Signed-off-by: Diana Popa <dpopa@amazon.com>

Signed-off-by: Diana Popa <dpopa@amazon.com>

Expose signal value of siginfo_t

Currently exposes it for following platforms:

- Linux has it as enum _timer and it is exposed alongside sigval
- On FreeBSD like systems si_value follows after si_addr (according to headers)
- Darwin is similar to FreeBSD
- NetBSD and FreeBSD uses struct that contains pid, uid, and si_value. Exposed via it

P.s. I'd like to take a look at other platforms too, but these are what I know so far.
FreeBSD needs some testing though

cc @gnzlbg

Exposes value for most unix like platforms

Bump patch version

Remove AF_MAX, PF_MAX, NET_MAXID constants

These constants have already been deprecated for a few releases with
a deprecation notice, so they can finally be removed.

Closes rust-lang/libc#665

Reduce appveyor churn

This should reduce the Appveyorn churn for other projects a bit more.

Please let me know if there is anything else that can be done. Maybe the infra team could discuss whether to document some general guidelines for rust-lang and rust-lang-nursery projects, and write them down somewhere. I would be willing to help.

cc @RalfJung @Mark-Simulacrum

Update ctest version

The latest ctest version enabled the ABI roundtrip test by default, in which we initialize all types in Rust by default to some random bit-pattern, pass them to C, verify, modify, pass back to Rust, and verify.

This catches issues in the call ABI / calling convention.

This PR will silence those here for now.

These constants have already been deprecated for a few releases with
a deprecation notice, so they can finally be removed.

Closes rust-lang/libc#665

Fix link in README.md

Same as #1417, but actually against the right branch this time.

wasi: add c_schar definition

This fixes an issue when building https://github.com/capstone-rust/capstone-rs/ for WASI.

Otherwise, I get:
~~~
error[E0412]: cannot find type `c_schar` in module `libc`
 --> /home/user/capstone-rs/target/wasm32-wasi/debug/build/capstone-sys-1019f1f8759b0d05/out/capstone.rs:4:27
  |
4 | pub type __int8_t = libc::c_schar;
  |                           ^^^^^^^ help: a type alias with a similar name exists: `c_char`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0412`.
error: Could not compile `capstone-sys`.
~~~

The file with the error is generated with bindgen:

https://github.com/capstone-rust/capstone-rs/blob/a74126cd88d683c0c16029be361ee85c12934878/capstone-sys/pre_generated/capstone.rs#L3-L5

Remove new field from ucontext_t for compatibility with earlier glibc versions

Per discussion in #1410 with @gnzlbg, this is necessary to avoid struct size mismatches between Rust and C on systems with glibc < 2.28.

Add RTM_* constants to linux/mod.rs for rtnetlink

There is one last set of constants I'm looking to get added to libc for rtnetlink support in my netlink library. I'm going to follow this up with a release PR once this PR is merged.