Opaque OrdinalPool.getThreadR.

Lemma updThread_internal_execution:
forall tp tp' m m' i j xs c pmap
(cnti: containsThread tp i)
(cnti': containsThread tp' i)
(Hinv: invariant (updThread cnti c pmap))
(Hcomp' : mem_compatible (updThread cnti c pmap) m)
(Hneq: i <> j)
(Hexec: internal_execution [seq x <- xs | x == j] tp m tp' m'),
internal_execution [seq x <- xs | x == j] (updThread cnti c pmap) m
(updThread cnti' c pmap) m'.