Support types in Foreign module

[HaskellZhangSong]

support pretty print for the types in Foreign.C.Types, Foreign.Ptr, Foreign.C.String.

[sjakobi]

To be clear: You'd like to get Pretty instances (and potentially PrettyAnn instances) for these types, right?

• Foreign.C.Types seems to contain about 20 newtypes.
• Foreign.Ptr exports Ptr, FunPtr, IntPtr and WordPtr
• In Foreign.C.String I can only find a few type synonyms, but no newtypes or or datatypes that we could define instances for.

What kind of behaviour / output would you expect for the new instances?