Missing types for `fx+/wraparound` and friends

[LiberalArtist]

Here's a motivating example, inspired by the discussion on Discord:

#lang typed/racket/base

(: fib (-> Nonnegative-Fixnum Nonnegative-Fixnum))
(define (fib n)
  (let loop ([n : Nonnegative-Fixnum n]
             [prev : Nonnegative-Fixnum 0]
             [cur  : Nonnegative-Fixnum 1])
    (cond
      [(= n 0)
       prev]
      [(= n 1)
       cur]
      [else
       (loop (- n 1)
             cur
             (abs (fx+/wraparound prev cur)))])))

;; Shouldn't need this!
(require typed/racket/unsafe)
(unsafe-require/typed
 racket/unsafe/ops
 [(unsafe-fxabs abs) (-> Fixnum Nonnegative-Fixnum)]
 [(unsafe-fx+/wraparound fx+/wraparound) (-> Fixnum Fixnum Fixnum)])

Maybe there should be a CI test for certain modules that all of their functions have type information?