Add Directory file descriptor relative syscall.

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.

.travis.yml

@@ -18,6 +18,7 @@ script:
       cargo build --no-default-features &&
       rustc ci/style.rs && ./style src;
     fi
+osx_image: xcode7.3
 os:
   - linux
   - osx

src/unix/bsd/apple/mod.rs

@@ -1365,6 +1365,33 @@ extern {
     pub fn querylocale(mask: ::c_int, loc: ::locale_t) -> *const ::c_char;
     pub fn getpriority(which: ::c_int, who: ::id_t) -> ::c_int;
     pub fn setpriority(which: ::c_int, who: ::id_t, prio: ::c_int) -> ::c_int;
+
+    pub fn openat(dirfd: ::c_int, pathname: *const ::c_char,
+                  flags: ::c_int, ...) -> ::c_int;
+    pub fn faccessat(dirfd: ::c_int, pathname: *const ::c_char,
+                     mode: ::c_int, flags: ::c_int) -> ::c_int;
+    pub fn fchmodat(dirfd: ::c_int, pathname: *const ::c_char,
+                    mode: ::mode_t, flags: ::c_int) -> ::c_int;
+    pub fn fchownat(dirfd: ::c_int, pathname: *const ::c_char,
+                    owner: ::uid_t, group: ::gid_t,
+                    flags: ::c_int) -> ::c_int;
+    #[cfg_attr(target_os = "macos", link_name = "fstatat$INODE64")]
+    pub fn fstatat(dirfd: ::c_int, pathname: *const ::c_char,
+                   buf: *mut stat, flags: ::c_int) -> ::c_int;
+    pub fn linkat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                  newdirfd: ::c_int, newpath: *const ::c_char,
+                  flags: ::c_int) -> ::c_int;
+   pub fn mkdirat(dirfd: ::c_int, pathname: *const ::c_char,
+                  mode: ::mode_t) -> ::c_int;
+   pub fn readlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                     buf: *mut ::c_char, bufsiz: ::size_t) -> ::ssize_t;
+   pub fn renameat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                   newdirfd: ::c_int, newpath: *const ::c_char)
+                   -> ::c_int;
+   pub fn symlinkat(target: *const ::c_char, newdirfd: ::c_int,
+                    linkpath: *const ::c_char) -> ::c_int;
+   pub fn unlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                   flags: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

src/unix/bsd/freebsdlike/mod.rs

@@ -753,6 +753,36 @@ extern {
                                  stacksize: *mut ::size_t) -> ::c_int;
     pub fn getpriority(which: ::c_int, who: ::c_int) -> ::c_int;
     pub fn setpriority(which: ::c_int, who: ::c_int, prio: ::c_int) -> ::c_int;
+
+    pub fn openat(dirfd: ::c_int, pathname: *const ::c_char,
+                  flags: ::c_int, ...) -> ::c_int;
+    pub fn faccessat(dirfd: ::c_int, pathname: *const ::c_char,
+                     mode: ::c_int, flags: ::c_int) -> ::c_int;
+    pub fn fchmodat(dirfd: ::c_int, pathname: *const ::c_char,
+                    mode: ::mode_t, flags: ::c_int) -> ::c_int;
+    pub fn fchownat(dirfd: ::c_int, pathname: *const ::c_char,
+                    owner: ::uid_t, group: ::gid_t,
+                    flags: ::c_int) -> ::c_int;
+    pub fn fstatat(dirfd: ::c_int, pathname: *const ::c_char,
+                   buf: *mut stat, flags: ::c_int) -> ::c_int;
+    pub fn linkat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                  newdirfd: ::c_int, newpath: *const ::c_char,
+                  flags: ::c_int) -> ::c_int;
+   pub fn mkdirat(dirfd: ::c_int, pathname: *const ::c_char,
+                  mode: ::mode_t) -> ::c_int;
+   pub fn mknodat(dirfd: ::c_int, pathname: *const ::c_char,
+                 mode: ::mode_t, dev: dev_t) -> ::c_int;
+   pub fn readlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                     buf: *mut ::c_char, bufsiz: ::size_t) -> ::ssize_t;
+   pub fn renameat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                   newdirfd: ::c_int, newpath: *const ::c_char)
+                   -> ::c_int;
+   pub fn symlinkat(target: *const ::c_char, newdirfd: ::c_int,
+                    linkpath: *const ::c_char) -> ::c_int;
+   pub fn unlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                   flags: ::c_int) -> ::c_int;
+   pub fn mkfifoat(dirfd: ::c_int, pathname: *const ::c_char,
+                   mode: ::mode_t) -> ::c_int;
 }
 
 cfg_if! {

src/unix/bsd/openbsdlike/mod.rs

@@ -476,6 +476,36 @@ extern {
                    winp: *mut ::winsize) -> ::pid_t;
     pub fn getpriority(which: ::c_int, who: ::id_t) -> ::c_int;
     pub fn setpriority(which: ::c_int, who: ::id_t, prio: ::c_int) -> ::c_int;
+
+    pub fn openat(dirfd: ::c_int, pathname: *const ::c_char,
+                  flags: ::c_int, ...) -> ::c_int;
+    pub fn faccessat(dirfd: ::c_int, pathname: *const ::c_char,
+                     mode: ::c_int, flags: ::c_int) -> ::c_int;
+    pub fn fchmodat(dirfd: ::c_int, pathname: *const ::c_char,
+                    mode: ::mode_t, flags: ::c_int) -> ::c_int;
+    pub fn fchownat(dirfd: ::c_int, pathname: *const ::c_char,
+                    owner: ::uid_t, group: ::gid_t,
+                    flags: ::c_int) -> ::c_int;
+    pub fn fstatat(dirfd: ::c_int, pathname: *const ::c_char,
+                   buf: *mut stat, flags: ::c_int) -> ::c_int;
+    pub fn linkat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                  newdirfd: ::c_int, newpath: *const ::c_char,
+                  flags: ::c_int) -> ::c_int;
+   pub fn mkdirat(dirfd: ::c_int, pathname: *const ::c_char,
+                  mode: ::mode_t) -> ::c_int;
+   pub fn mknodat(dirfd: ::c_int, pathname: *const ::c_char,
+                 mode: ::mode_t, dev: dev_t) -> ::c_int;
+   pub fn readlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                     buf: *mut ::c_char, bufsiz: ::size_t) -> ::ssize_t;
+   pub fn renameat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                   newdirfd: ::c_int, newpath: *const ::c_char)
+                   -> ::c_int;
+   pub fn symlinkat(target: *const ::c_char, newdirfd: ::c_int,
+                    linkpath: *const ::c_char) -> ::c_int;
+   pub fn unlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                   flags: ::c_int) -> ::c_int;
+   pub fn mkfifoat(dirfd: ::c_int, pathname: *const ::c_char,
+                   mode: ::mode_t) -> ::c_int;
 }
 
 cfg_if! {

src/unix/notbsd/linux/mod.rs

@@ -627,6 +627,10 @@ extern {
                              remote_iov: *const ::iovec,
                              riovcnt: ::c_ulong,
                              flags: ::c_ulong) -> isize;
+
+    // Not available now on Android
+    pub fn mkfifoat(dirfd: ::c_int, pathname: *const ::c_char,
+                    mode: ::mode_t) -> ::c_int;
 }
 
 cfg_if! {

src/unix/notbsd/mod.rs

@@ -804,6 +804,34 @@ extern {
     pub fn stat64(path: *const c_char, buf: *mut stat64) -> ::c_int;
     pub fn eventfd(init: ::c_uint, flags: ::c_int) -> ::c_int;
     pub fn sysinfo (info: *mut ::sysinfo) -> ::c_int;
+
+    pub fn openat(dirfd: ::c_int, pathname: *const ::c_char,
+                  flags: ::c_int, ...) -> ::c_int;
+    pub fn faccessat(dirfd: ::c_int, pathname: *const ::c_char,
+                     mode: ::c_int, flags: ::c_int) -> ::c_int;
+    pub fn fchmodat(dirfd: ::c_int, pathname: *const ::c_char,
+                    mode: ::mode_t, flags: ::c_int) -> ::c_int;
+    pub fn fchownat(dirfd: ::c_int, pathname: *const ::c_char,
+                    owner: ::uid_t, group: ::gid_t,
+                    flags: ::c_int) -> ::c_int;
+    pub fn fstatat(dirfd: ::c_int, pathname: *const ::c_char,
+                   buf: *mut stat, flags: ::c_int) -> ::c_int;
+    pub fn linkat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                  newdirfd: ::c_int, newpath: *const ::c_char,
+                  flags: ::c_int) -> ::c_int;
+   pub fn mkdirat(dirfd: ::c_int, pathname: *const ::c_char,
+                  mode: ::mode_t) -> ::c_int;
+   pub fn mknodat(dirfd: ::c_int, pathname: *const ::c_char,
+                 mode: ::mode_t, dev: dev_t) -> ::c_int;
+   pub fn readlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                     buf: *mut ::c_char, bufsiz: ::size_t) -> ::ssize_t;
+   pub fn renameat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                   newdirfd: ::c_int, newpath: *const ::c_char)
+                   -> ::c_int;
+   pub fn symlinkat(target: *const ::c_char, newdirfd: ::c_int,
+                    linkpath: *const ::c_char) -> ::c_int;
+   pub fn unlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                   flags: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

src/unix/solaris/mod.rs

@@ -911,5 +911,35 @@ extern {
     pub fn getloadavg(loadavg: *mut ::c_double, nelem: ::c_int) -> ::c_int;
     pub fn getpriority(which: ::c_int, who: ::c_int) -> ::c_int;
     pub fn setpriority(which: ::c_int, who: ::c_int, prio: ::c_int) -> ::c_int;
+
+    pub fn openat(dirfd: ::c_int, pathname: *const ::c_char,
+                  flags: ::c_int, ...) -> ::c_int;
+    pub fn faccessat(dirfd: ::c_int, pathname: *const ::c_char,
+                     mode: ::c_int, flags: ::c_int) -> ::c_int;
+    pub fn fchmodat(dirfd: ::c_int, pathname: *const ::c_char,
+                    mode: ::mode_t, flags: ::c_int) -> ::c_int;
+    pub fn fchownat(dirfd: ::c_int, pathname: *const ::c_char,
+                    owner: ::uid_t, group: ::gid_t,
+                    flags: ::c_int) -> ::c_int;
+    pub fn fstatat(dirfd: ::c_int, pathname: *const ::c_char,
+                   buf: *mut stat, flags: ::c_int) -> ::c_int;
+    pub fn linkat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                  newdirfd: ::c_int, newpath: *const ::c_char,
+                  flags: ::c_int) -> ::c_int;
+   pub fn mkdirat(dirfd: ::c_int, pathname: *const ::c_char,
+                  mode: ::mode_t) -> ::c_int;
+   pub fn mknodat(dirfd: ::c_int, pathname: *const ::c_char,
+                 mode: ::mode_t, dev: dev_t) -> ::c_int;
+   pub fn readlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                     buf: *mut ::c_char, bufsiz: ::size_t) -> ::ssize_t;
+   pub fn renameat(olddirfd: ::c_int, oldpath: *const ::c_char,
+                   newdirfd: ::c_int, newpath: *const ::c_char)
+                   -> ::c_int;
+   pub fn symlinkat(target: *const ::c_char, newdirfd: ::c_int,
+                    linkpath: *const ::c_char) -> ::c_int;
+   pub fn unlinkat(dirfd: ::c_int, pathname: *const ::c_char,
+                   flags: ::c_int) -> ::c_int;
+   pub fn mkfifoat(dirfd: ::c_int, pathname: *const ::c_char,
+                   mode: ::mode_t) -> ::c_int;
 }