I only added "*at" syscall relative to Posix2008 specification.

At the moment OSX and Android are partially supporting this API.

This include:
* `openat`
* `faccessat`
* `fchmodat`
* `fchownat`
* `fstatat`
* `linkat`
* `mkdirat`
* `mknodat` [0]
* `readlinkat`
* `renameat`
* `symlinkat`
* `unlinkat`
* `mkfifoat` [0][1]

[1] Not available on Android at the moment:
* `mkfifo`

[1] Not available on OSX at the moment:
* `mkfifoat`
* `mknodat`

And exclude operating system specific API:
* `renameat2`: Linux specific
* `execveat`: Linux specific since 3.19
* `futimesat`: GNU extension
* `name_to_handle_at`: GNU extension
* `scandirat`: GNU extension
* `fanotify_mark`: belong to fanotify API.

Fix ioctl types for non-x86 musl

This fixes up #289 by changing the type for other platforms as well.

added const SOCK_SEQPACKET,  and SOCK_RDM where applicable

... which is used for UNIX Seqpacket sockets as well as SCTP IP.

I have verified in source on  a couple Linux flavours as well as freebsd and darwin source that SOCK_SEQPACKET has value 5.
Solaris is the odd one with a value of 6.  I also added RDM for solaris (value 5)

Added nice, setpriority and getpriority along with constants and type…

… definitions

Adding sysinfo() and sysinfo struct for Linux and Android.

Sadly, the sysinfo struct varies slightly between Musl and Glibc / Bionic.

This means that users need to be careful when using the uptime, and should
always cast it to a signed value. Why uptime can be signed is beyond me...

Add pthread mutex type constants

These are needed to create a pthread mutex that doesn't use lock elision on glibc.

linux: Support getting and setting the cpu affinity for the current pthread.

This implements `pthread_getaffinity_np` and `pthread_setaffinity_np` for linux.

pthread.

Sadly, the sysinfo struct varies slightly between Musl and Glibc / Bionic.

This means that users need to be careful when using the uptime, and should
always cast it to a signed value. Why uptime can be signed is beyond me...

Add the TIOCGWINSZ and TIOCSWINSZ constants

I've added the `TIOCGWINSZ` and `TIOCSWINSZ` constants/ioctl control codes. I wasn't quite sure where to put them, so hopefully they're in the right place.

As of now it's set to compile on 'FreeBSD-like' platforms, so it will compile on both FreeBSD *and* DragonflyBSD. I've only tested it on FreeBSD though, but it should also work on DragonflyBSD AFAIK.

Fixes #292.

Fix ioctl constants for musl target envs.

Heya!

I ran across this issue today while trying to build a portable static binary using the `x86_64-unknown-linux-musl` target. Took a bit of digging to make sure I understood what was going on, and while I may still be off the mark, I believe this is a fix to my issue.

Thanks!!

----

According to musl's source, the `ioctl` [function signature][musl-ioctl-h] takes an `int` as the request argument (i.e. an `i32`) which is reflected in this crate's [ioctl binding][musl-ioctl-rs]. It looks like when the ioctl constants were added that [glibc's default][glibc-ioctl-h] of a `c_ulong` type was used for the musl values as well, rather than a `c_int` type. This change updates these constants to a `c_int` so that they match the expected function call type.

Here is a minimal reproduction of the issue. Given this Rust program:

```rust
extern crate libc;

use libc::{ioctl, winsize, STDOUT_FILENO, TIOCGWINSZ};

fn main() {
    let mut wsize = winsize {
        ws_row: 0,
        ws_col: 0,
        ws_xpixel: 0,
        ws_ypixel: 0,
    };
    unsafe {
        ioctl(STDOUT_FILENO, TIOCGWINSZ, &mut wsize);
    }
    println!("Sizes: {{ rows: {}, cols: {}, xpixel: {}, ypixel: {} }}",
             wsize.ws_row,
             wsize.ws_col,
             wsize.ws_xpixel,
             wsize.ws_ypixel);
}
```

When run against the `x86_64-unknwon-linux-gnu` and
`x86_64-unknown-linux-musl` targets, we see the difference in behavior:

```
> cargo clean

> cargo run --target=x86_64-unknown-linux-gnu
   Compiling libc v0.2.11
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
     Running `target/x86_64-unknown-linux-gnu/debug/libc-musl-ioctl`
Sizes: { rows: 28, cols: 211, xpixel: 0, ypixel: 0 }

> cargo clean

> cargo run --target=x86_64-unknown-linux-musl
   Compiling libc v0.2.11
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
src/main.rs:13:30: 13:40 error: mismatched types:
 expected `i32`,
    found `u64` [E0308]
src/main.rs:13         ioctl(STDOUT_FILENO, TIOCGWINSZ, &mut wsize);
                                            ^~~~~~~~~~
src/main.rs:13:30: 13:40 help: run `rustc --explain E0308` to see a detailed explanation
error: aborting due to previous error
Could not compile `libc-musl-ioctl`.

To learn more, run the command again with --verbose.
```

Working against this fix:

```
> cargo clean

> cargo run --target=x86_64-unknown-linux-gnu
    Updating git repository `https://github.com/fnichol/rust-lang-libc.git`
   Compiling libc v0.2.11 (https://github.com/fnichol/rust-lang-libc.git?branch=fix-musl-ioctl-constants#3285f387)
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
     Running `target/x86_64-unknown-linux-gnu/debug/libc-musl-ioctl`
Sizes: { rows: 28, cols: 211, xpixel: 0, ypixel: 0 }

> cargo clean

> cargo run --target=x86_64-unknown-linux-musl
   Compiling libc v0.2.11 (https://github.com/fnichol/rust-lang-libc.git?branch=fix-musl-ioctl-constants#3285f387)
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
     Running `target/x86_64-unknown-linux-musl/debug/libc-musl-ioctl`
Sizes: { rows: 28, cols: 211, xpixel: 0, ypixel: 0 }
```

[musl-ioctl-rs]:
https://doc.rust-lang.org/libc/x86_64-unknown-linux-musl/libc/fn.ioctl.html

[musl-ioctl-h]:
https://git.musl-libc.org/cgit/musl/tree/include/sys/ioctl.h

[glibc-ioctl-h]:
http://bazaar.launchpad.net/~vcs-imports/glibc/master/view/head:/include/sys/ioctl.h

Add back HW_NCPU

Removed by accident in #285

Removed by accident in #285

According to musl's source, the `ioctl` [function
signature][musl-ioctl-h] takes an `int` as the request argument (i.e. an
`i32`) which is reflected in this crate's [ioctl
binding][musl-ioctl-rs]. It looks like when the ioctl constants were
added that [glibc's default][glibc-ioctl-h] of a `c_ulong` type was used
for the musl values as well, rather than a `c_int` type. This change
updates these constants to a `c_int` so that they match the expected
function call type.

Here is a minimal reproduction of the issue. Given this Rust program:

```rust
extern crate libc;

use libc::{ioctl, winsize, STDOUT_FILENO, TIOCGWINSZ};

fn main() {
    let mut wsize = winsize {
        ws_row: 0,
        ws_col: 0,
        ws_xpixel: 0,
        ws_ypixel: 0,
    };
    unsafe {
        ioctl(STDOUT_FILENO, TIOCGWINSZ, &mut wsize);
    }
    println!("Sizes: {{ rows: {}, cols: {}, xpixel: {}, ypixel: {} }}",
             wsize.ws_row,
             wsize.ws_col,
             wsize.ws_xpixel,
             wsize.ws_ypixel);
}
```

When run against the `x86_64-unknwon-linux-gnu` and
`x86_64-unknown-linux-musl` targets, we see the difference in behavior:

```
> cargo clean

> cargo run --target=x86_64-unknown-linux-gnu
   Compiling libc v0.2.11
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
     Running `target/x86_64-unknown-linux-gnu/debug/libc-musl-ioctl`
Sizes: { rows: 28, cols: 211, xpixel: 0, ypixel: 0 }

> cargo clean

> cargo run --target=x86_64-unknown-linux-musl
   Compiling libc v0.2.11
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
src/main.rs:13:30: 13:40 error: mismatched types:
 expected `i32`,
    found `u64` [E0308]
src/main.rs:13         ioctl(STDOUT_FILENO, TIOCGWINSZ, &mut wsize);
                                            ^~~~~~~~~~
src/main.rs:13:30: 13:40 help: run `rustc --explain E0308` to see a detailed explanation
error: aborting due to previous error
Could not compile `libc-musl-ioctl`.

To learn more, run the command again with --verbose.
```

Working against this fix:

```
> cargo clean

> cargo run --target=x86_64-unknown-linux-gnu
    Updating git repository `https://github.com/fnichol/rust-lang-libc.git`
   Compiling libc v0.2.11 (https://github.com/fnichol/rust-lang-libc.git?branch=fix-musl-ioctl-constants#3285f387)
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
     Running `target/x86_64-unknown-linux-gnu/debug/libc-musl-ioctl`
Sizes: { rows: 28, cols: 211, xpixel: 0, ypixel: 0 }

> cargo clean

> cargo run --target=x86_64-unknown-linux-musl
   Compiling libc v0.2.11 (https://github.com/fnichol/rust-lang-libc.git?branch=fix-musl-ioctl-constants#3285f387)
   Compiling libc-musl-ioctl v0.1.0 (file:///src/libc-musl-ioctl)
     Running `target/x86_64-unknown-linux-musl/debug/libc-musl-ioctl`
Sizes: { rows: 28, cols: 211, xpixel: 0, ypixel: 0 }
```

[musl-ioctl-rs]:
https://doc.rust-lang.org/libc/x86_64-unknown-linux-musl/libc/fn.ioctl.html

[musl-ioctl-h]:
https://git.musl-libc.org/cgit/musl/tree/include/sys/ioctl.h

[glibc-ioctl-h]:
http://bazaar.launchpad.net/~vcs-imports/glibc/master/view/head:/include/sys/ioctl.h

Don't link util on musl, consolidate #[link]

Added extensive constants to make use of the BSD's sysctl function.

sysctl usage does differ significantly across the BSDs, and, whilst
some constants overlap, many do not. It is easier to maintain them
in separate modules, rather than trying to tease out common definitions.

sysctl usage does differ significantly across the BSDs, and, whilst
some constants overlap, many do not. It is easier to maintain them
in separate modules, rather than trying to tease out common definitions.

Add notbsd process_vm_readv and process_vm_writev system calls

Added getloadavg for Linux, the BSDs and Solaris.

Sadly Android's bionic lacks this functionality.

Sadly Android's bionic lacks this functionality.

Getprogname

Added `getprogname()` and `setprogname()` for all BSDs and Solaris (including Mac OS X).

Added `program_invocation_short_name` global, for Linux (glibc and Musl) which is effectively the same thing, and is what compatibility libraries like `libbsd` use to implement `getprogname()`.

Added `__progname` global for Android, which, whilst not quite the same as `getprogname` or `program_invocation_short_name`, is better than using argv[0], as it (a) avoids a common bug with no arguments (b) avoids a common bug with a NULL string in argv[0] and (c) incorporates Android's chosen name for an unknown process.

Adding program_invocation_short_name for Linux (Musl and glibc).

Adding __progname for Android. This is a little different, but
is a safer alternative to using argv[0], which may not exist, and
includes Android's default application name (currently '<unknown>').

Adding these functions and externs means it is possible for all
but Windows applications to safely discover their
name, rather than rely on argv[0] parsing, /proc/self/exe, etc.

Refine defininition of mcontext_t on linux glibc x86-64 and x86.

Add correctly sized structs and types for Android aarch64.

So far both android x86_64 and aarch64 configurations used incorrect types from 32-bit architecture.

This PR updates only the aarch64, because it is more common. The x86_64 may be also incorrect, but is out of scope of this PR.