Missing instances

[pi8027]

• [x] nat_of_pos, nat_of_bin, pos_of_nat, and bin_of_nat (in ssrnat.v).
• [ ] fact_rec and factorial (in ssrnat.v).
• [ ] operators for finite ordinals (in fintype.v).
• [ ] prime, logn, pdiv, max_pdiv, and totient (in prime.v).
• [ ] up_log (in prime.v, available only from MathComp 1.14.0, see math-comp/math-comp#823).
• [ ] binomial_rec, binomial, ffact_rec, and falling_factorial (in binomial.v).
• [ ] Order.min and Order.max for natdvd (in order.v).
• [ ] Order.lteif and Order.leif for bool, nat, natdvd, and int (in order.v and ssrint.v).
• [ ] exprz for int (in ssrint.v).
• [ ] operators for rational numbers (in rat.v).