Add definitions for unistd

unistd/src/lib.rs

@@ -4,11 +4,26 @@ extern crate libc;
 
 use libc::*;
 
+pub const NULL: c_int = 0;
+
 pub const R_OK: c_int = 1;
 pub const W_OK: c_int = 2;
 pub const X_OK: c_int = 4;
 pub const F_OK: c_int = 8;
 
+pub const SEEK_SET: c_int = 0;
+pub const SEEK_CUR: c_int = 1;
+pub const SEEK_END: c_int = 2;
+
+pub const F_ULOCK: c_int = 0;
+pub const F_LOCK: c_int = 1;
+pub const F_TLOCK: c_int = 2;
+pub const F_TEST: c_int = 3;
+
+pub const STDIN_FILENO: c_int = 0;
+pub const STDOUT_FILENO: c_int = 1;
+pub const STDERR_FILENO: c_int = 2;
+
 #[no_mangle]
 pub extern "C" fn _exit(status: c_int) {
     unimplemented!();