i686-apple-darwin and other 32bit Apple targets ware demoted to tier-3 due
to lack of support from the vendor, and is no longer available from rustup
for nightly, shortly beta.

DockerOSX32 job was removed as it only tests on nightly. BuildChannelsOSX job
will continue testing on these targets on older compilers (stable and below).

Add Redox FD_* function-macros and Android AI_* constants

I'm not sure if I'm allowed to add multiple, separate APIs in the same PR, but I guess they're both for uncommon/exotic platforms?

The `AI_*` constants were taken from `usr/include/netdb.h` on my Termux install; the `FD_` functions were taken from `linux_like/mod.rs`.

Add dlmopen dlinfo and related consts.

I actually have no idea if the constants I copied from my computer are cross-platform.

Solarish: Fix utmx Debug impl and re-add support for extra traits

Fix a bug where the compilation failed cause `utmpx.host` is bigger than 32 so we cannot print it.

Due to a break of compilation (only with extra trait enabled) on a Tier 2 platform, I do think it would be better to do another release as soon as proven fixing compilation

Add sock_extended_err and associated constants from errqueue.h to linux_like

This is an alternate version of #1614 that attempts to fix issues with the android ctests by rearranging the headers.  Due to long CI cycle time, I've opened it as an alternate PR.  Only one or the other should merge, depending if linux_like or linux is the correct place for this.

sock_extended_err is a struct returned as a control message when the sockopt
IP_RECVERR is set, when recvmsg has the MSG_ERRQUEUE flag set. IP_RECVERR and
MSG_ERRQUEUE are constants both already defined here.

Update bindings for the wasm32-wasi target

This commit performs a number of updates for libc with the `wasm32-wasi`
target:

* Updates the `wasi-libc` repository commit used (previously known as
  `wasi-sysroot`)
* Updates the container to Ubuntu 19.10 which has Clang 9 packaged which
  is all we need.
* Avoids building `wasmtime` and instead downloads a precompiled binary.
* Updates bindings in `src/wasi.rs` to match the current upstream state.

Modelled after the cmsg tests, this wraps the C macro into a function, and then
compares the results to the Rust implementation in libc.

sock_extended_err is a struct returned as a control message when the sockopt
IP_RECVERR is set, when recvmsg has the MSG_ERRQUEUE flag set.  IP_RECVERR and
MSG_ERRQUEUE are constants both already defined here.

This moves the linux/ headers after others
This keeps the Android tests closer to the Linux ones.
I think this is needed to get linux/errqueue.h to not cause compilation
failures.

Implement utmp for NetBSD

Followed this: https://github.com/NetBSD/src/blob/trunk/include/utmp.h

use *const pointer for NetBSD's pthread_setname_np

Add ucred and socket related types to uclibc-mips32

Fix compilation of the [tokio](https://github.com/tokio-rs) rust for MIPS architecture when using uClibc. Added missed types, which are defined in library headers:
https://github.com/kraj/uClibc/blob/ca1c74d67dd115d059a875150e10b8560a9c35a8/libc/sysdeps/linux/common/bits/socket.h#L320
https://github.com/kraj/uClibc/blob/ca1c74d67dd115d059a875150e10b8560a9c35a8/libc/sysdeps/linux/common/bits/in.h#L35-L36
https://github.com/kraj/uClibc/blob/ca1c74d67dd115d059a875150e10b8560a9c35a8/libc/sysdeps/linux/common/bits/in.h#L140-L143

Should also solve https://github.com/rust-lang-nursery/net2-rs/issues/88

Revisit of #1500

Implement utmpx.h itens for NetBSD

This PR partially closes #1534

If add the constants, structs and and extra traid implmentation

Add support for shared memory operations for solaris/illumos

This is needed because Firefox now uses slice-deque rust crate.

expose futimens() for illumos systems

illumos has an implementation of `futimens()` which we should expose.  I'm working on a broader set of [fixes for illumos](https://github.com/rust-lang/libc/compare/master...jclulow:illumos_fixes) in general, but that's going to take a lot more work to be ready so the test suite doesn't currently seem to function.

Support for RISC-V 64-bit GNU/Linux

Add support for RISC-V 64-bit GNU/Linux.

Follow up to rust-lang/rust#66661.

r? @alexcrichton