std: Expand the area of std::fs

This commit is an implementation of [RFC 1044][rfc] which adds additional
surface area to the `std::fs` module. All new APIs are `#[unstable]` behind
assorted feature names for each one.

[rfc]: https://github.com/rust-lang/rfcs/pull/1044

The new APIs added are:

* `fs::canonicalize` - bindings to `realpath` on unix and
  `GetFinalPathNameByHandle` on windows.
* `fs::symlink_metadata` - similar to `lstat` on unix
* `fs::FileType` and accessor methods as `is_{file,dir,symlink}`
* `fs::Metadata::file_type` - accessor for the raw file type
* `fs::DirEntry::metadata` - acquisition of metadata which is free on Windows
  but requires a syscall on unix.
* `fs::DirEntry::file_type` - access the file type which may not require a
  syscall on most platforms.
* `fs::DirEntry::file_name` - access just the file name without leading
  components.
* `fs::PathExt::symlink_metadata` - convenience method for the top-level
  function.
* `fs::PathExt::canonicalize` - convenience method for the top-level
  function.
* `fs::PathExt::read_link` - convenience method for the top-level
  function.
* `fs::PathExt::read_dir` - convenience method for the top-level
  function.
* `std::os::raw` - type definitions for raw OS/C types available on all
  platforms.
* `std::os::$platform` - new modules have been added for all currently supported
  platforms (e.g. those more specific than just `unix`).
* `std::os::$platform::raw` - platform-specific type definitions. These modules
  are populated with the bare essentials necessary for lowing I/O types into
  their raw representations, and currently largely consist of the `stat`
  definition for unix platforms.

This commit also deprecates `Metadata::{modified, accessed}` in favor of
inspecting the raw representations via the lowering methods of `Metadata`.

src/libstd/os/linux/raw.rs

@@ -0,0 +1,170 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Linux-specific raw type definitions
+
+pub type dev_t = u64;
+pub type mode_t = u32;
+
+#[doc(inline)]
+pub use self::arch::{off_t, ino_t, nlink_t, blksize_t, blkcnt_t, stat, time_t};
+
+#[cfg(any(target_arch = "x86",
+          target_arch = "le32",
+          target_arch = "powerpc",
+          target_arch = "arm"))]
+mod arch {
+    use super::{dev_t, mode_t};
+    use os::raw::{c_long, c_short};
+    use os::unix::raw::{gid_t, uid_t};
+
+    pub type blkcnt_t = i32;
+    pub type blksize_t = i32;
+    pub type ino_t = u32;
+    pub type nlink_t = u32;
+    pub type off_t = i32;
+    pub type time_t = i32;
+
+    #[repr(C)]
+    pub struct stat {
+        pub st_dev: dev_t,
+        pub __pad1: c_short,
+        pub st_ino: ino_t,
+        pub st_mode: mode_t,
+        pub st_nlink: nlink_t,
+        pub st_uid: uid_t,
+        pub st_gid: gid_t,
+        pub st_rdev: dev_t,
+        pub __pad2: c_short,
+        pub st_size: off_t,
+        pub st_blksize: blksize_t,
+        pub st_blocks: blkcnt_t,
+        pub st_atime: time_t,
+        pub st_atime_nsec: c_long,
+        pub st_mtime: time_t,
+        pub st_mtime_nsec: c_long,
+        pub st_ctime: time_t,
+        pub st_ctime_nsec: c_long,
+        pub __unused4: c_long,
+        pub __unused5: c_long,
+    }
+}
+
+#[cfg(any(target_arch = "mips",
+          target_arch = "mipsel"))]
+mod arch {
+    use super::{dev_t, mode_t};
+    use os::raw::c_long;
+    use os::unix::raw::{gid_t, uid_t};
+
+    pub type blkcnt_t = i32;
+    pub type blksize_t = i32;
+    pub type ino_t = u32;
+    pub type nlink_t = u32;
+    pub type off_t = i32;
+    pub type time_t = i32;
+
+    #[repr(C)]
+    pub struct stat {
+        pub st_dev: c_ulong,
+        pub st_pad1: [c_long; 3],
+        pub st_ino: ino_t,
+        pub st_mode: mode_t,
+        pub st_nlink: nlink_t,
+        pub st_uid: uid_t,
+        pub st_gid: gid_t,
+        pub st_rdev: c_ulong,
+        pub st_pad2: [c_long; 2],
+        pub st_size: off_t,
+        pub st_pad3: c_long,
+        pub st_atime: time_t,
+        pub st_atime_nsec: c_long,
+        pub st_mtime: time_t,
+        pub st_mtime_nsec: c_long,
+        pub st_ctime: time_t,
+        pub st_ctime_nsec: c_long,
+        pub st_blksize: blksize_t,
+        pub st_blocks: blkcnt_t,
+        pub st_pad5: [c_long; 14],
+    }
+}
+
+#[cfg(target_arch = "aarch64")]
+mod arch {
+    use super::{dev_t, mode_t};
+    use os::raw::{c_long, c_int};
+    use os::unix::raw::{gid_t, uid_t};
+
+    pub type blkcnt_t = i64;
+    pub type blksize_t = i32;
+    pub type ino_t = u64;
+    pub type nlink_t = u32;
+    pub type off_t = i64;
+    pub type time_t = i64;
+
+    #[repr(C)]
+    pub struct stat {
+        pub st_dev: dev_t,
+        pub st_ino: ino_t,
+        pub st_mode: mode_t,
+        pub st_nlink: nlink_t,
+        pub st_uid: uid_t,
+        pub st_gid: gid_t,
+        pub st_rdev: dev_t,
+        pub __pad1: dev_t,
+        pub st_size: off_t,
+        pub st_blksize: blksize_t,
+        pub __pad2: c_int,
+        pub st_blocks: blkcnt_t,
+        pub st_atime: time_t,
+        pub st_atime_nsec: c_long,
+        pub st_mtime: time_t,
+        pub st_mtime_nsec: c_long,
+        pub st_ctime: time_t,
+        pub st_ctime_nsec: c_long,
+        pub __unused: [c_int; 2],
+    }
+}
+
+#[cfg(target_arch = "x86_64")]
+mod arch {
+    use super::{dev_t, mode_t};
+    use os::raw::{c_long, c_int};
+    use os::unix::raw::{gid_t, uid_t};
+
+    pub type blkcnt_t = i64;
+    pub type blksize_t = i64;
+    pub type ino_t = u64;
+    pub type nlink_t = u64;
+    pub type off_t = i64;
+    pub type time_t = i64;
+
+    #[repr(C)]
+    pub struct stat {
+        pub st_dev: dev_t,
+        pub st_ino: ino_t,
+        pub st_nlink: nlink_t,
+        pub st_mode: mode_t,
+        pub st_uid: uid_t,
+        pub st_gid: gid_t,
+        pub __pad0: c_int,
+        pub st_rdev: dev_t,
+        pub st_size: off_t,
+        pub st_blksize: blksize_t,
+        pub st_blocks: blkcnt_t,
+        pub st_atime: time_t,
+        pub st_atime_nsec: c_long,
+        pub st_mtime: time_t,
+        pub st_mtime_nsec: c_long,
+        pub st_ctime: time_t,
+        pub st_ctime_nsec: c_long,
+        pub __unused: [c_long; 3],
+    }
+}