Fix 'renamed lint' warnings

src/libstd/sys/common/mod.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![allow(missing_doc)]
+#![allow(missing_docs)]
 #![allow(dead_code)]
 
 use io::{mod, IoError, IoResult};

src/libstd/sys/unix/mod.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![allow(missing_doc)]
+#![allow(missing_docs)]
 #![allow(non_camel_case_types)]
 #![allow(unused_imports)]
 #![allow(dead_code)]

src/libstd/sys/windows/mod.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![allow(missing_doc)]
+#![allow(missing_docs)]
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
 #![allow(unused_imports)]