* The `flock` structure has an extra field
* Some `flock`-related constants have different value
* Some constants like `TABN` don't exist
* The `fsblkcnt_t` and `fsfilcnt_t` type definitions are u64 for x86_64 FreeBSD
* The `d_namelen` field in `dirent` was renamed correctly to `d_namlen`
* The alignment of `fd_set` was off, and the macros were updated to not always
  assume a 32-bit integer is used.

This commit adds support to test all libc definitions on both OpenBSD and
FreeBSD via QEMU userspace emulation. Specially prepared images for each OS are
used which are essentially intended to run a script on startup and then exit.
Documentation has been added to the `ci/README.md` file describing this new
system.

Adjust MIPS MS_RMT_MASK to match <sys/mount.h>.

Signed-off-by: David Henningsson <diwic@ubuntu.com>

It's got a new toolchain which should hopefully support some more modern
definitions.

This is a blanket import of lots of constants and function from nix-rust

This should help the repo be resilient to ctest changes upstream.

 See https://github.com/rust-lang-nursery/libc/pull/50 for details

They're all added under the `foo64` names with the `foo64` types added as well,
so they still need to be explicitly chosen.

Fixup the value of PTHREAD_STACK_MIN as well

Extracted tests!