Panic when using syb with GHC API

[Simon Hengel]

Hi Pedro,

> If it seems like this avoids the problem, I'd be happy to release a
> new version of SYB containing these type-guided traversals.

Do you think it would be a good idea to make the interfaces of
Data.Generics.GPS and Data.Generics more similar?  One thing I have
noted is, that Data.Generics exports Data.Data, but Data.Generics.GPS
does not.

Cheers,
Simon