Fix item::is_of_ammo_type_or_contains_it.

Make it recursive as it is supposed to be.

Don't use `item::ammo_type`, as this returns the ammo type that is used (if it is a gun/tool/gunmod), and the ammo type if the item is actually ammo.

Reported at http://smf.cataclysmdda.com/index.php?topic=5885