devel/hs-QuickCheck: Update to 2.15

QuickCheck 2.15
* BREAKING: properties without quantification are no longer implicitly
  wrapped in once
* Add witness property modifier and witnesses field in result on
compilers that support Typeable to allow conveniently exposing
counterexamples
* Add assertException, assertExceptionIO, assertDeepException, and
assertDeepExceptionIO (thanks to Alexey Kuleshevich)
* Add withMaxSize, withMaxShrinks, and withMaxDiscardRatio combinators
* Add recheck
* Add HasCallStack to partial top-level functions
* Updated some documentation
* Fix overflow bug when calculating discard ratio
* Fix error printing bug when shrinks are discarded
* Fix withMaxSuccess not working when checkCoverage is turned on
* Fix a bug whereby an unfortunately timed discard could unduly fail a
property running with checkCoverage
* Fix Arbitrary intance for Map breaking invariants from
Data.Map.Strict (thanks to Neil Mayhew)
* Fix non-covered classes not showing up in output as 0% covered
* Fix Negative's Arbitrary instance discarding an unnecessary number
of generated values.
* Fix promote doing an unnecessary seed split
* Fix a bug whereby maxSuccess and discardRatio would interact poorly
to produce too few size increases.
* Fix a couple of underflow bugs in generators for Small Natural and
Ratio Natural
* Fix a bug whereby the internal DISCARDED exception would show up
user-side in sample

(pho)