ocaml: phase 6 List.equal / List.compare (+5 tests, 589 total)

Both take an inner predicate / comparator and walk both lists in
lockstep:

  equal eq a b     short-circuits on first mismatch
  compare cmp a b  -1 if a is a strict prefix
                    1 if b is
                    0 if both empty
                    otherwise first non-zero element comparison

Mirrors real OCaml's signatures.

  List.equal (=) [1;2;3] [1;2;3]            = true
  List.equal (=) [1;2;3] [1;2;4]            = false
  List.compare compare [1;2;3] [1;2;4]      = -1
  List.compare compare [1;2] [1;2;3]        = -1
  List.compare compare [] []                = 0

lib/ocaml/runtime.sx

@@ -194,6 +194,24 @@
          | Some v -> Some v
          | None -> find_map f t
 
+     let rec equal eq a b =
+       match a with
+       | [] -> (match b with [] -> true | _ -> false)
+       | h :: t ->
+         (match b with
+          | [] -> false
+          | h2 :: t2 -> if eq h h2 then equal eq t t2 else false)
+
+     let rec compare cmp a b =
+       match a with
+       | [] -> (match b with [] -> 0 | _ -> -1)
+       | h :: t ->
+         (match b with
+          | [] -> 1
+          | h2 :: t2 ->
+            let c = cmp h h2 in
+            if c <> 0 then c else compare cmp t t2)
+
      let rec combine xs ys =
        match xs with
        | [] -> (match ys with