Transparent Mem.storebytes.

Lemma storebytes_val_obs:
forall (mc mc' mf : mem) (f:memren)
(b1 b2 : block) (ofs: Z) mv1 mv2
(Hstore: Mem.storebytes mc b1 ofs mv1 = Some mc')
(Hf: f b1 = Some b2)
(Hval_obs_eq: list_forall2 (fun a b => memval_obs_eq f a b) mv1 mv2)
(Hobs_eq: mem_obs_eq f mc mf),
exists mf',
Mem.storebytes mf b2 ofs mv2 = Some mf' /\
mem_obs_eq f mc' mf'.