Added PrimBytes instances for C-types.

[Rotaerk]

To resolve #20, added the GeneralizedNewtypeDeriving and TypeInType extensions, imported Foreign.C.Types, and added a deriving instance PrimBytes for every C-type.

[achirkin]

Great, thanks! Could you please change a few small things in Numeric.PrimBytesTest?

• Either remove CBool test or suppress the orphan instance warning in the file.
• Add couple random variants to type TypeTriples
• Add couple variants to type SamePrimRepTypes. These may be any pairs of types containing ({CType wrapper} <-> {underlying type}), e.g. '(Double, CDouble), or '(Either Word8 Int64, Either CBool CLLong) (just select such that the underlying type independent of a platform x64/x32).

[Rotaerk]

How's this?

[achirkin]

Cool! Sorry I forgot about SamePrimRep boilerplate