I would like to have a test that determines if a particular function is Listable.  In the case of Symbols this is merely a matter of checking `Attributes`.  `Function` definitions with the `Listable` attribute are a bit more involved but quite easy.

**However I specifically want to test for *inherent listability* in as many cases as possible.**

For example consider the function from **Case #4** in https://mathematica.stackexchange.com/questions/7924/alternatives-to-procedural-loops-and-iterating-over-lists-in-mathematica:

    (3 - #)/(7 * #) &

This function is *inherently listable*:

    fn = (3 - #)/(7*#) &;
    Map[fn, {1, 2, 3}]
    fn @ {1, 2, 3}

>     {2/7, 1/14, 0}
>     {2/7, 1/14, 0}

- One must consider Functions with multiple arguments, both the `Slot` and named parameter type.

- Ideally the test would handle pattern-based (DownValues) functions to the extent that is possible.