[haskell-gnuplot] Exposing Terminal.C and Display.C

[Alex Lang]

I think it would be nice to expose Graphics.Gnuplot.Terminal.C and
Graphics.Gnuplot.Display.C.
I am trying to write a function which does some string parsing and
returns a terminal, but I cannot write a type signature for it unless
Terminal.C is exposed.

Any thoughts?

Thanks,
Alex