Goal:
    A : Type  p : A → bool  l : list A
  ============================
   (Forall (λ x : A, p x) l ↔ forallb p l)


DEBUG:Going to execute:
split
DEBUG LTAC Evaluated term: (map_id l)
DEBUG LTAC Evaluated term: (map_id l)
DEBUG LTAC Evaluated term: forall_map_spec