ocaml: phase 5.1 exception_user.ml baseline (user exception with payload, 4+5+7+10 = 26)

Defines a user exception with int payload:

  exception Negative of int

  let safe_sqrt n =
    if n < 0 then raise (Negative n)
    else <integer sqrt via while loop>

  let try_sqrt n =
    try safe_sqrt n with
    | Negative x -> -x

  try_sqrt  16  -> 4
  try_sqrt  25  -> 5
  try_sqrt -7   -> 7  (handler returns -(-7) = 7)
  try_sqrt 100  -> 10
  sum           -> 26

Tests exception declaration with int payload, raise with carry, and
try-with arm pattern-matching the constructor with payload binding.

56 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -15,6 +15,7 @@
   "coin_change.ml": 6,
   "csv.ml": 10,
   "exception_handle.ml": 4,
+  "exception_user.ml": 26,
   "expr_eval.ml": 16,
   "expr_simp.ml": 22,
   "factorial.ml": 3628800,