Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  Γ : list A
  H : All2_fold P Γ Γ
  ============================
   (All_fold (λ (Γ : list A) (d : A), P Γ Γ d d) Γ)


DEBUG:Going to execute:
fun tac H =>
             try intros until H; intro_block H;
              (try simpl in H; DepElim.simplify_equations_in H);
              DepElim.generalize_by_eqs_vars H; CoreTactics.block_goal; 
              tac H; CoreTactics.intros_until_block; DepElim.simpl_dep_elim;
              CoreTactics.unblock_goal