ocaml: phase 5.1 euler1.ml baseline (Project Euler #1, multiples of 3 or 5 below 1000 = 233168)

Project Euler #1: sum of all multiples of 3 or 5 below 1000.

  let euler1 limit =
    let sum = ref 0 in
    for i = 1 to limit - 1 do
      if i mod 3 = 0 || i mod 5 = 0 then sum := !sum + i
    done;
    !sum

  euler1 1000 = 233168

Trivial DSL exercise but symbolically meaningful: this is the 100th
baseline program.

100 baseline programs total — milestone.

lib/ocaml/baseline/expected.json

@@ -24,6 +24,7 @@
   "csv.ml": 10,
   "exception_handle.ml": 4,
   "exception_user.ml": 26,
+  "euler1.ml": 233168,
   "expr_eval.ml": 16,
   "expr_simp.ml": 22,
   "factorial.ml": 3628800,