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.

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

Support calls to the SunOS Doors API

Doors are a lightweight IPC mechanism available in libc on Solaris & illumos. They are like unix domain sockets, but faster and more pleasant to work with.

* Brief introduction: ["Doors" in SolarisTM: Lightweight RPC using File Descriptors](http://www.kohala.com/start/papers.others/doors.html)
* Relevant manual pages: [DOOR_CALL(3C)](https://illumos.org/man/3C/door_call), [DOOR_CREATE(3C)](https://illumos.org/man/3C/door_create)
* Tutorial I wrote: ["Revolving Doors": A tutorial on the Illumos Doors API](https://github.com/robertdfrench/revolving-door)

Marking this as a draft until I have included the full api.

Add ttyname_r

I hope this is correct. Parameter types taken from `man ttyname`.

```c
int ttyname_r(int fd, char *buf, size_t buflen);
```

Add cfg_attr

haiku: add missing ioctl identifiers to control the TTY

Ref. [termios.h](https://github.com/haiku/haiku/blob/37761761a0c93a96c47d7cfb72f80ab56a8c1722/headers/posix/termios.h#L165-L189)

Add getrandom() bindings on Linux

Closes #659