Auto merge of #2270 - RalfJung:futex-ordering, r=RalfJung
Auto merge of #2270 - RalfJung:futex-ordering, r=RalfJung

test that futexes induce appropriate synchronization

This fails when I remove the `validate_lock_acquire` or `validate_lock_release` from `futex_wake`. So finally we got those code paths actually covered in tests. :)

rust-lang/miri,rust-lang/miri,rust-lang/miri,rust-lang/miri