Handle some stabilized rustc features

pcid/src/main.rs

@@ -1,6 +1,3 @@
-// Already stabilized, TODO: remove when Redox's rustc is updated
-#![feature(result_option_inspect)]
-
 use std::fs::{File, metadata, read_dir};
 use std::io::prelude::*;
 use std::os::unix::io::{FromRawFd, RawFd};