message: also test std::hint::spin_loop
diff: -#![feature(rustc_private)]
  +#![feature(rustc_private, renamed_spin_loop)]
  use std::sync::{Mutex, TryLockError};
  use std::sync::atomic;
  +use std::hint;
  fn main() {
  test_mutex_stdlib();
  @@ -56,6 +57,7 @@ impl<T> TryLockErrorExt<T> for TryLockError<T> {
  fn test_spin_loop_hint() {
  atomic::spin_loop_hint();
  + hint::spin_loop();
  }
  fn test_thread_yield_now() {
  