Start new cities with 5,000 units of food, since we're dealing with larger numbers now.
Make number fields wider - they can now accomodate 7-digit numbers (up to 9,999,999).
When setting colors in Interface::minister_food(), make sure there's a default option - otherwise old colors may persist (e.g. the red of 0 fields worked would persist even if you start working some fields).  Interface::list_farm_crops() multiplies the food production list by the farm building's field_output to precisely indicate how much food we'll reap by planting this crop.