Opaque containsThread.

(** [FineConc.MachStep] preserves [spinlock_synchronized]*)
Lemma fineConc_step_synchronized:
forall U0 U U'  tr tp0 m0 tp m tp' m' tr'
(Hexec: multi_fstep (U0, [::], tp0) m0 (U, tr, tp) m)
(Hstep: fstep (U, tr, tp) m (U', tr ++ tr', tp') m')
(Hsynchronized: spinlock_synchronized tr),
spinlock_synchronized (tr ++ tr').