Transparent Mem.loadbytes.

Lemma loadbytes_val_obs:
forall (mc mf : mem) (f:memren)
(b1 b2 : block) (ofs sz : Z) mv
(Hsz: sz >= 0)
(Hload: Mem.loadbytes mc b1 ofs sz = Some mv)
(Hf: f b1 = Some b2)
(Hinjective: forall b0 b1' b3 : block, f b0 = Some b3 -> f b1' = Some b3 -> b0 = b1')
(Hobs_eq: strong_mem_obs_eq f mc mf),
exists mv',
Mem.loadbytes mf b2 ofs sz = Some mv' /\
list_forall2 (fun a b => memval_obs_eq f a b) mv mv'.