ocaml: phase 5.1 newton_sqrt.ml baseline (Newton's method, sqrt(2)*1000 = 1414)

Newton's method for square root:

  let sqrt_newton x =
    let g = ref 1.0 in
    for _ = 1 to 20 do
      g := (!g +. x /. !g) /. 2.0
    done;
    !g

20 iterations is more than enough to converge for x=2 — result is
~1.414213562. Multiplied by 1000 and int_of_float'd: 1414.

First baseline exercising:
  - for _ = 1 to N do ... done (wildcard loop variable)
  - pure float arithmetic with +. /.
  - the int_of_float truncate-toward-zero fix from iter 117

38 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -23,6 +23,7 @@
   "memo_fib.ml": 75025,
   "merge_sort.ml": 44,
   "module_use.ml": 3,
+  "newton_sqrt.ml": 1414,
   "mutable_record.ml": 10,
   "option_match.ml": 5,
   "pi_leibniz.ml": 314,