small compatibility shim for older versions of transformers.

 This package includes backported versions of types that were added
 to transformers in transformers 0.3 an 0.4 for users who need strict
 transformers 0.2 or 0.3 compatibility to run on old versions of the
 platform, but also need those types.
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.