* cheating by starting to unload and after getting paid rushing to the depot to get sold (or unloading, loading and getting paid again for the remainder)
* cargo being dropped onto a station at the moment a stockpiling industry doesn't accept it anymore
* industries getting cargo that has not been unloaded yet and subsequently dumping it back on the station in one go
Note: you will now get paid after the unloading has finished, so you'll have to wait a bit longer for 'your' money.
This will allow to perform more changes per month on big maps and less on smaller maps, while not overtaxing the IndustryMonthlyLoop process.
Thanks to frosch, for nice code ideas and rewrites
