ocaml: phase 5.1 partition.ml baseline (stable partition, evens*100 + odds = 3025)

Two ref lists accumulating in reverse, then List.rev'd — preserves
original order:

  let partition pred xs =
    let yes = ref [] in
    let no = ref [] in
    List.iter (fun x ->
      if pred x then yes := x :: !yes
      else no := x :: !no
    ) xs;
    (List.rev !yes, List.rev !no)

  partition (fun x -> x mod 2 = 0) [1..10]
  -> ([2;4;6;8;10], [1;3;5;7;9])

  evens sum * 100 + odds sum = 30 * 100 + 25 = 3025

Tests higher-order predicate, tuple return, and iter-98 let-tuple
destructuring on the call site.

108 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -74,6 +74,7 @@
   "option_match.ml": 5,
   "palindrome.ml": 4,
   "paren_depth.ml": 7,
+  "partition.ml": 3025,
   "pancake_sort.ml": 910,
   "pascal.ml": 252,
   "peano.ml": 30,