Optimize getting last list element

See: goblint#966 (comment), goblint#966 (comment),
goblint#966 (comment)

Author: gabryon99

src/cdomains/intDomain.ml

@@ -1252,9 +1252,9 @@ struct
   | [], _ -> [] | _ ,[] -> xs
   | _, _ ->
     let min_xs = fst (List.hd xs) in
-    let max_xs = snd (List.hd (List.rev xs)) in
+    let max_xs = snd @@ BatList.last xs in
     let min_ys = fst (List.hd ys) in
-    let max_ys = snd (List.hd (List.rev ys)) in
+    let max_ys = snd @@ BatList.last ys in
     let min_range,max_range = range ik in
     let min = if Ints_t.compare min_xs min_range == 0 then min_ys else min_xs in
     let max = if Ints_t.compare max_xs max_range == 0 then max_ys else max_xs in
@@ -1282,7 +1282,9 @@ struct
 
   let minimal = function [] -> None | (x, _)::_ -> Some x
 
-  let maximal xs = xs |> List.rev |> (function [] -> None | (_, y)::_ -> Some y)
+  let maximal = function
+    | [] -> None
+    | xs ->  let last = BatList.last xs |> snd in Some last
 
   let of_interval ik (x, y) = norm ik @@ Some (x, y)