`Small` has no `CoArbitrary` instance

[andreasabel]

When trying to use $allProperties on a prop_Foo that uses type Small Int:

No instance for ‘CoArbitrary (Small Int)’
        arising from a use of ‘property’

Is there a reason why Small cannot have a CoArbitrary instance?

[MaximilianAlgehed]

@nick8325 unless there is some reason for this that I can't make sense of I'm going to add instances of CoArbitrary and Function for the types in Test.QuickCheck.Modifiers.