ocaml: phase 5.1 euler36.ml baseline (sum of double-base palindromes <= 1000 = 1772)

Numbers that read the same in base 10 and base 2:

  1, 3, 5, 7, 9, 33, 99, 313, 585, 717
  sum = 1772

Implementation:
  pal_dec n        check decimal palindrome via index walk
  to_binary n      build binary string via mod 2 / div 2 stack
  pal_bin n        check binary palindrome
  euler36 limit    scan 1..limit-1, sum where both palindromes

Real PE36 uses 10^6 (answer 872187). 1000 takes ~9 minutes on
contended host but stays within reasonable budget for the
spec-level evaluator.

123 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -36,6 +36,7 @@
   "euler29_small.ml": 15,
   "euler30_cube.ml": 1301,
   "euler34_small.ml": 145,
+  "euler36.ml": 1772,
   "euler40_small.ml": 15,
   "euler3.ml": 29,
   "euler4_small.ml": 9009,