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.

Add Illumos support

Add setns api to linux targets

Adds setns libc api to all linux targets

Signed-off-by: Jana Radhakrishnan <mrjana@gmail.com>

Add powerpc64 and powerpc64le support

A number of libc constants are different on PowerPC64 Linux, so push
them down into arch specific files.

Skip C/Rust type checks for eventfd.

Correct MIPS types of SA_* flags

Missed out correction from 6ac75c16

libc-test's C program should not #include <linux/fs.h> on Linux

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

Merging a number of PRs into one

See: http://developer.android.com/ndk/downloads/revision_history.html

The `net2` crate currently fails to cross-compile to Android with
``error: unresolved name `libc::SO_REUSEPORT` ``

According to http://stackoverflow.com/a/14388707/1162888,
Android is essentially the same as Linux for the purpose of
socket features support, and the Linux kernel has supported
`SO_REUSEPORT` since version 3.9.

According to http://android.stackexchange.com/a/51656,
Android has had more recent kernels than that since version 4.4 Kit Kat.

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

SYS_entropy is internal and may more easily change than getentropy(2).

- under openbsd/bitrig it is 256
- change type to `size_t` where system have `getnameinfo()` with
  `hostlen` as `size_t`

under openbsd it is a `caddr_t` which expand to `char *`.
as the size of the type change, adjust the padding too.