This library is there to ensure compatibility with QCheck 0.8 and earlier.
It has a unique module QCheck_runner that merges the custom runners
from qcheck-core.runner (QCheck_base_runner)
and the OUnit runners from qcheck-ounit (QCheck_ounit)
into a single module.
By depending on qcheck-core, this library also brings QCheck in scope,
so it can be used transparently.