message: use references so that potential aliasing bugs are triggered during regression test
diff: +// compile-flags: -Zmiri-track-raw-pointers
  #![feature(new_uninit)]
  #![feature(slice_as_chunks)]
  #![feature(slice_partition_dedup)]
  @@ -220,13 +221,23 @@ fn test_for_invalidated_pointers() {
  // Calls `fn as_chunks_unchecked_mut` internally (requires unstable `#![feature(slice_as_chunks)]`):
  assert_eq!(2, buffer.as_chunks_mut::<32>().0.len());
  + for chunk in buffer.as_chunks_mut::<32>().0 {
  + for elem in chunk {
  + *elem += 1;
  + }
  + }
  // Calls `fn split_at_mut_unchecked` internally:
  let split_mut = buffer.split_at_mut(32);
  assert_eq!(split_mut.0, split_mut.1);
  // Calls `fn partition_dedup_by` internally (requires unstable `#![feature(slice_partition_dedup)]`):
  - assert_eq!(1, buffer.partition_dedup().0.len());
  + let partition_dedup = buffer.partition_dedup();
  + assert_eq!(1, partition_dedup.0.len());
  + partition_dedup.0[0] += 1;
  + for elem in partition_dedup.1 {
  + *elem += 1;
  + }
  buffer.rotate_left(8);
  buffer.rotate_right(16);
  