Fix the initialization of the soliterator type.
Fix the initialization of the soliterator type.

In Python 3, the type of `soliterator` was incorrectly being set to
`soliterator` itself, rather than just `type`. In addition, we
were forgetting to call PyType_Ready.

ContinuumIO/pycosat,ContinuumIO/pycosat,sandervandorsten/pycosat,sandervandorsten/pycosat