ocaml: phase 5.1 dp_word_break.ml baseline (4/5 strings segmentable)

Classic word-break DP — for each position i, check whether any
dictionary word ends at i with a prior reachable position:

  dp[i] = exists w in dict with wl <= i and
          dp[i - wl] && s.sub (i - wl) wl = w

Dictionary: apple, pen, pine, pineapple, cats, cat, and, sand, dog
Inputs:
  applepenapple        yes  (apple pen apple)
  pineapplepenapple    yes  (pineapple pen apple)
  catsanddog           yes  (cats and dog)
  catsandog            no   (no segmentation reaches the end)
  applesand            yes  (apple sand)

Tests bool-typed Array, String.sub primitive, nested List.iter
over the dict inside for-loop over end positions, closure capture
of the outer dp.

179 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -35,6 +35,7 @@
   "csv.ml": 10,
   "egg_drop.ml": 8,
   "dijkstra.ml": 7,
+  "dp_word_break.ml": 4,
   "distinct_subseq.ml": 3,
   "exception_handle.ml": 4,
   "exception_user.ml": 26,