It turns out that you do need to use callbacks to fetch all item
information from the server.  Modify the update code to listen for
ITEM_DATA_LOAD_RESULT events to execute a callback to properly
update an equipped item.

Change the way that `Ovale_EquipmentChanged` is fired by always
including the slot name that has been changed.  The event now fires
whenever ITEM_DATA_LOAD_RESULT returns success and the slot that
had a pending data load has been changed.

This avoids needing the 3-second delay kludge to wait for server
data.

Make all Ovale modules consistently use `ammoslot`, etc., instead
of `AMMOSLOT`, etc., to refer to the names of the equipment slots.
Make the conversion between the `SlotName` and `InventorySlotName`
types internal to the `Equipment` module.