Add ETH_* constants on Android

Adding ETH_* constants that were found here on Linux but not on Android.

Source Reference is [linux/if_ether.h](https://android.googlesource.com/platform/bionic/+/master/libc/kernel/uapi/linux/if_ether.h) on Google OpenSource.

Thank-you.

/cc nix-rust/nix#865

Add netlink structs to all notbsd platforms

Adding the remaining structs from `<linux/netlink.h>`. Sadly very duplicated, but that's how it ended up when added to all "notbsd" platforms except musl. If there is a better way to structure it to reduce duplication I'm all ears!

Prefer hexadecimal representation of O_TMPFILE on linux-sparc64

While working on the libc bindings for sparc-linux, I stumbled across this typo in the O_TMPFILE definition on linux-sparc64.

Compare with:

> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/sparc/bits/fcntl.h;hb=16efad5171ac1ac2c8728405f2703045f08c494b#l42
> https://sources.debian.org/src/glibc/2.26-6/sysdeps/unix/sysv/linux/sparc/bits/fcntl.h/#L42

CC @jrtc27

Add termios ioctl constants to NetBSD

These are all declared as `c_ulong` because that's what BSD's `ioctl()` function is declared with.

Add `IFF_*` constants  to linux, android and fuchsia

Add constants to android and fuchsia:

*    IFF_TUN
*    IFF_TAP
*    IFF_NO_PI

Type problem: https://github.com/rust-lang/libc/issues/915

so change constants type `libc::c_short` to `libc::c_int` :

*    IFF_*

add some sysv shared memory to macosx

Missing linux intrinsics

Add netfilter constants to Linux

Constants and enums from [`netfilter.h`] and [`nf_tables.h`].

I was not really sure what to do with the enums, for example `nf_tables_msg_types`. But since I could not find a C enum mapped into a Rust enum in this crate I assumed you wanted them as constants instead.

I also wanted to get the `nf_inet_addr` union in here. But I did not find any unions in this crate so I was not sure how you would prefer it represented.

There are of course a billion more netfilter constants and types to map. But this is a good start.

[`netfilter.h`]: https://github.com/torvalds/linux/blob/ead751507de86d90fa250431e9990a8b881f713c/include/uapi/linux/netfilter.h
[`nf_tables.h`]: https://github.com/torvalds/linux/blob/ead751507de86d90fa250431e9990a8b881f713c/include/uapi/linux/netfilter/nf_tables.h

Add posix_spawn bindings

Do not assume dynamic linking in musl/mips targets

Add missing FreeBSD APIs

Process descriptors, realtime process priority, a couple missing kqueue event filters.

Add syscall table for musl/powerpc64

CI still runs version 10

Available since FreeBSD 9.0, this API allows using local descriptors
instead of global PIDs. It works in Capsicum sandboxes.

add DT_UNKNOWN

The `d_type` field of `struct dirent` can be `DT_UNKNOWN` if a
filesystem doesn't support returning the file type in directory entries.
Linux's readdir(3) man page, for example, says: "Currently, only some
filesystems [...] have full support for returning the file type in
d_type. All applications must properly handle a return of DT_UNKNOWN."

The `d_type` field of `struct dirent` can be `DT_UNKNOWN` if a
filesystem doesn't support returning the file type in directory entries.
Linux's readdir(3) man page, for example, says: "Currently, only some
filesystems [...] have full support for returning the file type in
d_type. All applications must properly handle a return of DT_UNKNOWN."

Bsd domainname

Closes #868 .

Fix containers using ubuntu 17.04

Apparently 17.04 has gone away? Or updates are failing now?