stabalize infer outlives requirements (RFC 2093).

Co-authored-by: nikomatsakis

Author: toidiu

lib.rs

@@ -51,7 +51,6 @@
 // Handle rustfmt skips
 #![feature(custom_attribute)]
 #![cfg_attr(not(stage0), feature(nll))]
-#![cfg_attr(not(stage0), feature(infer_outlives_requirements))]
 #![allow(unused_attributes)]
 
 use std::io::prelude::*;