Auto merge of rust-lang#715 - goyox86:add-missing-constants-redox, r=alexcrichton

Add some permission and misc (mostly 'mode_t' related) constants to Redox.

Hi!

While porting some software ((exa)[https://github.com/ogham/exa])to Redox I found these missing constants.

Cheers!

//cc @ids1024 @jackpot51

Author: bors

src/redox.rs

@@ -52,6 +52,37 @@ pub const STDIN_FILENO: ::c_int = 0;
 pub const STDOUT_FILENO: ::c_int = 1;
 pub const STDERR_FILENO: ::c_int = 2;
 
+pub const EXIT_FAILURE: ::c_int = 1;
+pub const EXIT_SUCCESS: ::c_int = 0;
+
+pub const S_ISUID: ::c_int = 0x800;
+pub const S_ISGID: ::c_int = 0x400;
+pub const S_ISVTX: ::c_int = 0x200;
+
+pub const S_IFIFO: mode_t = 0x1000;
+pub const S_IFCHR: mode_t = 0x2000;
+pub const S_IFBLK: mode_t = 0x6000;
+pub const S_IFDIR: mode_t = 0x4000;
+pub const S_IFREG: mode_t = 0x8000;
+pub const S_IFLNK: mode_t = 0xA000;
+pub const S_IFSOCK: mode_t = 0xC000;
+pub const S_IFMT: mode_t = 0xF000;
+pub const S_IEXEC: mode_t = 0x40;
+pub const S_IWRITE: mode_t = 0x80;
+pub const S_IREAD: mode_t = 0x100;
+pub const S_IRWXU: mode_t = 0x1C0;
+pub const S_IXUSR: mode_t = 0x40;
+pub const S_IWUSR: mode_t = 0x80;
+pub const S_IRUSR: mode_t = 0x100;
+pub const S_IRWXG: mode_t = 0x38;
+pub const S_IXGRP: mode_t = 0x8;
+pub const S_IWGRP: mode_t = 0x10;
+pub const S_IRGRP: mode_t = 0x20;
+pub const S_IRWXO: mode_t = 0x7;
+pub const S_IXOTH: mode_t = 0x1;
+pub const S_IWOTH: mode_t = 0x2;
+pub const S_IROTH: mode_t = 0x4;
+
 extern {
     pub fn memalign(align: ::size_t, size: ::size_t) -> *mut ::c_void;
     pub fn read(fd: ::c_int, buf: *mut ::c_void, count: ::size_t)