Fix the dispatch test GC code under PyPy, and make the comment for Jython better.

if sys.platform.startswith('java'):

    def garbage_collect():

        """Run the garbage collector and wait a bit to let it do his work"""

        # Some JVM GCs will execute finalizers in a different thread, meaning

        # we need to wait for that to complete before we go on looking for the

        # effects of that.

        gc.collect()

        time.sleep(0.1)

elif hasattr(sys, "pypy_version_info"):

    def garbage_collect():

        # Collecting weakreferences can take two collections on PyPy.

        gc.collect()

        gc.collect()

else:

    def garbage_collect():

        gc.collect()