Try to shrink Prop Int values more effectively.
Try to shrink Prop Int values more effectively.

When shrinking (p :: Prop Int) now, we also try to relabel its PVar nodes
with integers in the range [0..length (vars p)].

The bound parameter in shrinkBoundProp actually seems to make a difference.
I guess I don't understand how QuickCheck does shrinking.

bradlarsen/hs-cudd,bradlarsen/hs-cudd,bradlarsen/hs-cudd