Transparent Mem.alloc.

Lemma mem_storebytes_cur :
forall b (ofs : Z) bytes (m m' : mem),
Mem.storebytes m b ofs bytes = Some m' ->
forall (b' : positive) (ofs' : Z),
(getCurPerm m) !! b' ofs' = (getCurPerm m') !! b' ofs'.