Automatically generating Unpeel instances for newtypes

[sweirich]

Many base module edit files include this for newtype coercions

add Data.Monoid Instance Unpeel_Dual a : Unpeel (Dual a) a :=
	 Build_Unpeel _ _ getDual Mk_Dual.

We shouldn't have to add these via an edit, though. Should just generate them whenever we see a newtype definition.