Ideally I'd like to remove quickCheckPure, quickCheckGenPure in favour of the new primed variants, but we've only just made a breaking release so perhaps we can do that next time.

After talking with @kritzcreek I'll revert the change to the implementation of the existing functions, and just add the new ones. The change means the existing function might perform slightly worse, since they'll accumulate all errors before printing the result, rather than just holding on to the first.