ocaml: phase 5.1 euler34_small.ml baseline (factorions <= 2000 = 145)

Number that equals the sum of factorials of its digits:
  145 = 1! + 4! + 5! = 1 + 24 + 120

Implementation:
  fact n           iterative factorial
  digit_fact_sum n walk digits, sum fact(digit)
  euler34 limit    scan 3..limit, accumulate matches

The only other factorion is 40585 = 4!+0!+5!+8!+5!. Real PE34 sums
both (= 40730); 2000 keeps under our search budget.

121 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -35,6 +35,7 @@
   "euler28.ml": 261,
   "euler29_small.ml": 15,
   "euler30_cube.ml": 1301,
+  "euler34_small.ml": 145,
   "euler3.ml": 29,
   "euler4_small.ml": 9009,
   "euler5.ml": 232792560,