Tool to produce dependency diagram from the set of *.hs files. Diagram
will include specified top-level declaration and all user-defined
types referencd from there (recursively).

To see dependency diagram for type MegaData and all other types
referenced from there, use:

        graphtype MegaData *.hs

User can choose to omit types and newtypes that do not contain
anything other than library types - this could be useful to unclutter
really large diagrams. Try running "graphtype --trim ..." and see
whether it helps you or otherwise.