ocaml: phase 5.1 expr_eval.ml baseline (9/9 pass)

A tiny arithmetic-expression evaluator using:
  type expr = Lit of int | Add of expr*expr | Mul of expr*expr | Neg of expr
  let rec eval e = match e with | Lit n -> n | Add (a,b) -> ...

Exercises type-decl + multi-arg ctor + recursive match end-to-end.
Per-program timeout in run.sh bumped to 120s.

lib/ocaml/baseline/run.sh

@@ -36,7 +36,7 @@ for f in lib/ocaml/baseline/*.ml; do
 (eval "(ocaml-run-program (file-read \"$f\"))")
 EOF
 
-  output=$(timeout 60 "$SX_SERVER" < "$TMP" 2>/dev/null)
+  output=$(timeout 120 "$SX_SERVER" < "$TMP" 2>/dev/null)
   rm -f "$TMP"
 
   result=$(echo "$output" | awk '