DeriveDataTypeable should be enabled in generated Abs.hs module (Haskell backend)

[fizruk]

Latest BNFC release broke generated Abs.hs modules.

DeriveDataTypeable is still needed to derive Data.

Originally posted by @fizruk in 8b1b96c

[fizruk]

This can be circumvented by enabling DeriveDataTypeable globally in a project, but I believe, it should be fixed in BNFC as well.

[andreasabel]

Oops. I botched this release.