ocaml: phase 5.1 hailstone.ml baseline (Collatz length from 27 = 111 steps)

Iterative Collatz / hailstone sequence:

  let collatz_length n =
    let m = ref n in
    let count = ref 0 in
    while !m > 1 do
      if !m mod 2 = 0 then m := !m / 2
      else m := 3 * !m + 1;
      count := !count + 1
    done;
    !count

27 is the famous 'long-running' Collatz starter. Reaches a peak of
9232 mid-sequence and takes 111 steps to bottom out at 1.

64 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -28,6 +28,7 @@
   "frequency.ml": 5,
   "gcd_lcm.ml": 60,
   "grep_count.ml": 3,
+  "hailstone.ml": 111,
   "hanoi.ml": 1023,
   "fizzbuzz.ml": 57,
   "flatten_tree.ml": 28,