Lift to let on lambdas should convert to normal functions

[gampleman]

Given:

example xs =
    List.map (\a -> a * 2) xs

when doing a lift to let on the lambda this currently results in

example xs =
    let
        var =
            (\a -> a * 2)
    in
        List.map var xs

but this would be preferable:

example xs =
    let
        fn a =
            a * 2
    in
        List.map fn xs