Constants for the linux nfqueue netlink protocol (userspace firewall).

Continuation of #1562 and #1571.

This triggers a warning on a recent nightly, which in turn breaks CI due to
`#![deny(warnings)]` in libc-test/build.rs

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.

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

Signed-off-by: patrick felt <patrick.felt@sling.com>

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

Fixes #1585

Signed-off-by: Arthur Gautier <baloo@gandi.net>

Signed-off-by: Arthur Gautier <baloo@gandi.net>

First batch for #1562

This adds libc-test support for Freebsd10 and a CI build job that tests
FreeBSD10 with LIBC_CI only.