Adding Fixed Point Data Types to base

[Michael Walker]

> All of the other utilities functions from these packages would not be moved to `base`; they would
> remain in `free`

Importing the types without the functions seems like people would
still end up depending on `free` to get those (or copy/paste the
definitions). I can understand not wanting to pull the `MonadFree`
typeclass and related functions into `base`, but there are a lot of
functions in `free` which don't depend on that but are still useful.

-- 
Michael Walker (http://www.barrucadu.co.uk)