time library dependencies

[Ashley Yakeley]

I'm looking to update the time library in response to various requests. 
Right now it has some weird split-base 2/3 dependency thing going on, 
and uses only FFI and CPP language extensions.

Will it cause anyone any problems if

* it depends >=base-4.1?
* it requires GeneralizedNewtypeDeriving and DeriveDataTypeable to build?

The Haskell language is kind of a moving target right now.

-- 
Ashley Yakeley