Save var_list_ used in stoch_simul to oo_

If variables are selected after stoch_simul, fields like oo_.var will be matrices of the dimension of var_list_. But the info on var_list_ is not stored. So if one loads results from a _results.mat-file, there is no way to recover to which variables the entries in oo_.var belong. The question is how to store this info as one can have several different stoch_simul-commands in a mod-file.