Run build test for `x86_64-unknown-redox`

Fix #1457

Android: Add preadv and pwritev.

From sys/uio.h. Note that preadv64/pwritev64 are already included in
src/unix/linux_like/mod.rs.

Add freebsd nmount

Adding FreeBSD's nmount call to mount devices on filesystems.  nmount is preferred over mount.

Drop FreeBSD 10 and add FreeBSD 13 image on Cirrus CI

This should fix our CI.

From sys/uio.h. Note that preadv64/pwritev64 are already included in
src/unix/linux_like/mod.rs.
Also fix parameter names of process_vm_[readv,writev] to match Bionic
header.

Revive `powerpc-unknown-linux-gnu` CI

Fix #1425

Revive `i686-linux-android` CI

Fixes #1765

Fix aarch64-linux-android target CI

Add deprecation notice to `af_alg_iv::as_slice` and trait implementations that depend on it

These trait implementations exposed an unsound API (see https://github.com/rust-lang/libc/issues/1501).

process_vm_readv, process_vm_writev should be available on android

process_vm_readv and process_vm_writev generally return -EPERM(-1) when used in android, however the syscalls work fine when running under privileged shell.
The following was tested(with modified nix) on Android 9/10 running Linux Kernel 4.9 on a SDM 845 phone:

```
fn read_mem_real(pid: i32, addr: usize, vsize: usize) -> Result<Vec<u8>, String> {
    let mut res = vec![0; vsize];
    let riovec: [RemoteIoVec; 1] = [RemoteIoVec {base: addr, len: vsize}];

    match process_vm_readv(Pid::from_raw(pid), &[IoVec::from_mut_slice(&mut res)], &riovec) {
        Err(e) => {
            log::info!("ERR {}", e);
            return Err(e.to_string());
        },
        Ok(_) => {
            return Ok(res);
        }
    }
}
```

This will work fine when run under su shell.

Signed-off-by: rupansh-arch <rupanshsekar@hotmail.com>

These trait implementations exposed an unsound API (see
https://github.com/rust-lang/libc/issues/1501)

Allow contributors to label issues via rustbot

Now bors suggests contributors label PRs with the status labels, e.g.:

https://github.com/rust-lang/libc/pull/1902#issuecomment-702337160

This allows it, and for issues as well.

Add clock_nanosleep to freebsd and netbsd

fixes #1921

Tweak GHA config to reduce bors time

So, "bors time" with the current config is slow a bit (~ 1h30m). We could reduce this by separating style check and docs generation, tweaking `max-parallel`, let's try it out!

Upload documentation to gh-pages from GHA

I missed this on #1918