Simplify scary logic around inventory item buttons.

[NQNStudios]

The logic that was causing #233 was marked as kludgy and in need of a redo. I've done that, and I think the new logic is more correct.

[CelticMinstrel]

1. Does this render ITEMBTN_NORM and ITEMBTN_ALL as entirely unused? If so, they can be deleted.
2. This doesn't break the ID / Ench / etc buttons, does it?

[NQNStudios]

I don't think so, but it needs testing. Incidentally, how would I make a party with an unidentified item? Edit a scenario and have them pick it up? Does the PC editor allow adding items? Should I just play the game until I find some? I do need to keep just testing VoDT so maybe that's what I'll do.

[CelticMinstrel]

The PC editor and the in-game debug mode both support adding items, but if I recall correctly, they automatically identify the items added. Probably the best way to get unidentified items is to enter a scenario and steal some stuff. (Picking stuff up off the ground is fine too, but those kinds of items often have the "Always Identified" flag.)

[NQNStudios]

• test can use items in combat, but not while targeting
• test doesn't break ID/Enchant/etc buttons
• see about removing ITEMBTN_NORM and ITEMBTN_ALL

[CelticMinstrel]

Just a note: the full list of buttons for point 2 is identify (ID), sell, enchant (Ench), and recharge (Inc).

[NQNStudios]

@CelticMinstrel I tested all those cases, I think it's good to go.