Add Morphism rsub with signature (req ==> req ==> req) as rsub_ext4.

(* Specifications: *)
Lemma same_genZ : forall x, [x] == gen_phiZ1 x.
Lemma gen_Zeqb_ok : forall x y, Zeq_bool x y = true -> [x] == [y].
Lemma gen_phiZ1_pos_sub : forall x y, gen_phiZ1 (Z.pos_sub x y) == gen_phiPOS1 x + -gen_phiPOS1 y.
Lemma gen_phiZ_add : forall x y, [x + y] == [x] + [y].
Lemma gen_phiZ_mul : forall x y, [x * y] == [x] * [y].
Lemma gen_phiZ_ext : forall x y : Z, x = y -> [x] == [y].
Lemma gen_phiZ_morph : ring_morph 0 1 radd rmul rsub ropp req Z0 (Zpos xH) Z.add Z.mul Z.sub Z.opp Zeq_bool gen_phiZ.
Lemma Nsth : Setoid_Theory N (@eq N).
Lemma Nseqe : sring_eq_ext N.add N.mul (@eq N).
Lemma Nth : semi_ring_theory 0%N 1%N N.add N.mul (@eq N).