fix build with QuickCheck 2.7.1

For some reason this was working w/o a cast before, despite POSIXTime etc
being newtypes. It stopped working with the new QuickCheck:

Utility/QuickCheck.hs:31:33:
    No instance for (Integral POSIXTime)
      arising from a use of `arbitrarySizedIntegral'
    Possible fix: add an instance declaration for (Integral POSIXTime)
    In the first argument of `nonNegative', namely
      `arbitrarySizedIntegral'
    In the expression: nonNegative arbitrarySizedIntegral
    In an equation for `arbitrary':
        arbitrary = nonNegative arbitrarySizedIntegral

0 files changed, 0 insertions, 0 deletions