Log Message:
devel/hs-witherable: update to witherable-0.5

0.5
---

* `FilterableWithIndex` is a superclass of `WitherableWithIndex`.
* Remove deprecated `Data.Witherable` module. Use `Witherable` module.
* Relax `FilterableWithIndex` composition law so list-like instances are lawful.
* Add `drain :: f a -> f b` method (with default implementation `drain = \ 
mapMaybe (Const Nothing)`) to the `Filterable`.