Fred utils: clean up comments, code and notation

No change in functionality
Fred attack utils: simplify parameters passed to functions

Use gamedata where several of its child tables are needed
Fred attack utils: fix bug (typo) in attack combo evaluation
Fred attack utils: clean up comments, code and notation

No change in functionality
Fred: remove spread_poison_eval()

It’s not being used anyway, and future implementations should be done
differently.
Fred: eliminate eval_grab_villages(), move content

into zone_action_villages().  There is really no point in having this
in a separate function.
Fred: adapt village grabbing to the new fred_utils functions

Next step in the general cleaning up and speeding up of the code.