ocaml: phase 5.1 kadane.ml baseline (max subarray sum = 6)

Kadane's algorithm in O(n):

  let max_subarray xs =
    let max_so_far = ref min_int in
    let cur = ref 0 in
    List.iter (fun x ->
      cur := max x (!cur + x);
      max_so_far := max !max_so_far !cur
    ) xs;
    !max_so_far

For [-2;1;-3;4;-1;2;1;-5;4] the optimal subarray is [4;-1;2;1] = 6.

Exercises min_int (iter 94), max as global, ref / ! / :=, and
List.iter with two side-effecting steps in one closure body.

46 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -21,6 +21,7 @@
   "fizzbuzz.ml": 57,
   "list_ops.ml": 30,
   "json_pretty.ml": 24,
+  "kadane.ml": 6,
   "lambda_calc.ml": 7,
   "levenshtein.ml": 11,
   "memo_fib.ml": 75025,

lib/ocaml/baseline/kadane.ml

@@ -0,0 +1,12 @@
+let max_subarray xs =
+  let max_so_far = ref min_int in
+  let cur = ref 0 in
+  List.iter (fun x ->
+    cur := max x (!cur + x);
+    max_so_far := max !max_so_far !cur
+  ) xs;
+  !max_so_far
+
+;;
+
+max_subarray [-2; 1; -3; 4; -1; 2; 1; -5; 4]