Remove unused files

Looks like these were missed in bf4e77d4.

src/libstd/sys/unix/helper_signal.rs

-// Copyright 2014 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.
-
-#![allow(deprecated)]
-
-use libc;
-use sys::os;
-
-use sys::fs::FileDesc;
-
-pub type signal = libc::c_int;
-
-pub fn new() -> (signal, signal) {
-    let (a, b) = unsafe { os::pipe().unwrap() };
-    (a.unwrap(), b.unwrap())
-}
-
-pub fn signal(fd: libc::c_int) {
-    FileDesc::new(fd, false).write(&[0]).unwrap();
-}
-
-pub fn close(fd: libc::c_int) {
-    let _fd = FileDesc::new(fd, true);
-}