Finished EmitCargoOnSell

The broken Lint check is still a problem after all those years. This also does not work as suggested in the empty trait. During selling it destroys the cargo so you can't just queue an Unload activity. You can't even enumerate through all passengers without hitting crashes. However, unloading just the first passenger is good enough for Red Alert's single-manned pillboxes.
This spawns all of the infantry at the center of the actor, which behaves badly as soon as you have multiple passengers (and presumably also if you have an even-sized footprint).

This should really:

* build a list of all the available subcells (each footprint cells * 5 subcells)
* pick one at random: discard it if full, otherwise spawn the infantry
* continue until there are no more passengers or no more subcells
* kill any remaining passengers.