Allow changing planner_discount in mod-file (preprocessor restriction)
See the discussion on the mailing list on 31/08/2015. This problem crashes the
Gali_discretion.mod unit test. My proposal is:
Treat the planner_discount option like any other option (or parameter for that matter) and allow resetting it via the same statement later on. If a warning is needed, I would provide a warning that the planner_discount has been updated. But I don't really see the need for this warning. Changing parameters is common.