adding forecast to estimation test with non-stationary variables

tests/kalman_filter_smoother/fs2000a.mod

@@ -79,5 +79,5 @@ Y_obs (gam);
 end;
 
 estimation(order=1,datafile=fsdat_simul,nobs=192,loglinear,mh_replic=0,
-           mode_compute=0,mh_nblocks=2,mh_drop=0.45,mh_jscale=0.65,diffuse_filter,smoother) P_obs gp_obs gy_obs;
+           mode_compute=4,mh_nblocks=2,mh_drop=0.45,mh_jscale=0.65,diffuse_filter,smoother,forecast=10) P_obs gp_obs gy_obs;