ocaml: phase 5.1 regex_simple.ml baseline (./* matcher, 7/28 match)

Recursive regex matcher with Leetcode-style semantics:
  .   matches any single character
  <c>* matches zero or more of <c>

  let rec is_match s i p j =
    if j = String.length p then i = String.length s
    else
      let first = i < String.length s
                  && (p.[j] = '.' || p.[j] = s.[i])
      in
      if j + 1 < String.length p && p.[j+1] = '*' then
           is_match s i p (j + 2)                   (* skip * group *)
        || (first && is_match s (i + 1) p j)        (* consume one  *)
      else
        first && is_match s (i + 1) p (j + 1)

Patterns vs texts:
  .a.b    | aabb axb "" abcd abc aaabbbc x   -> 1 match
  a.*b    | aabb axb "" abcd abc aaabbbc x   -> 2 matches
  x*      | aabb axb "" abcd abc aaabbbc x   -> 2 matches
  a*b*c   | aabb axb "" abcd abc aaabbbc x   -> 2 matches
                                             total = 7

Complements wildcard_match.ml which uses LIKE-style * / ?.

182 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -149,6 +149,7 @@
   "radix_sort.ml": 802002,
   "roman.ml": 44,
   "rolling_hash.ml": 6,
+  "regex_simple.ml": 7,
   "reverse_int.ml": 54329,
   "rpn.ml": 9,
   "run_decode.ml": 21,