Fix bug when calling non-Bayesian smoother after Bayesian estimation

Because xparam1 is used by the smoother, but xparam was set to the posterior mean, the non-Bayesian smoother results were based on the parameters at the mode, which are stored in xparam1.
Merge pull request #760 from JohannesPfeifer/fix_smoother

Fix bug when calling non-Bayesian smoother after Bayesian estimation