Opaque Mem.storebytes.

Lemma alloc_perm_eq:
forall f m m' lo hi m2 m2' b b'
(Hobs_eq: mem_obs_eq f m m')
(Halloc: Mem.alloc m lo hi = (m2, b))
(Halloc': Mem.alloc m' lo hi = (m2', b'))
b1 b2 ofs
(Hf: (if proj_sumbool (valid_block_dec m b1)
then f b1
else if proj_sumbool (valid_block_dec m2 b1)
then Some b' else None) = Some b2),
permission_at m2 b1 ofs Cur =
permission_at m2' b2 ofs Cur.