Export mkFun or Shrunk type

[coot]

Currently Shrunk type is not exported, and neither is mkFun (both are defined in Test.QuickCheck.Function), so the only hack to create something of the Fun type is to:

do
 Fun (_, _, notShrunk) _ <- arbitrary :: Gen (Fun a Bool)
 let fun = Fun (function (const False), False, notShrunked) (const False))

Which is rather cumbersome.