Merge from rustc

Author: RalfJung

src/lib.rs

@@ -7,7 +7,6 @@
 #![feature(yeet_expr)]
 #![feature(nonzero_ops)]
 #![feature(local_key_cell_methods)]
-#![feature(is_terminal)]
 #![feature(round_ties_even)]
 // Configure clippy and other lints
 #![allow(

tests/pass/shims/fs.rs

@@ -3,7 +3,6 @@
 
 #![feature(io_error_more)]
 #![feature(io_error_uncategorized)]
-#![feature(is_terminal)]
 
 use std::collections::HashMap;
 use std::ffi::{c_char, OsString};

tests/pass/shims/io.rs

@@ -1,5 +1,3 @@
-#![feature(is_terminal)]
-
 use std::io::IsTerminal;
 
 fn main() {