[issue1173] fix parameter order for MergeAndShrinkAlgorithm.

[speckdavid]

We passed the options for the merge_and_shrink evaluator into the constructor
of an internal class in the wrong order, leading to wrong behaviour. For example,
the boolean option prune_unreachable_states was interpreted as max_states,
so that max_states was set to 0 or 1 based on the boolean flag. This is now fixed.