Placed Charcoal Forge eats charcoal

[Barhandar]

As reported by MormonPartyboat here, the built charcoal forge code (f_forge) sets the charcoal amount to what's placed, instead of adding it.

Apparent relevant code:

https://github.com/CleverRaven/Cataclysm-DDA/blob/master/src/iexamine.cpp#L2331

if (amount != 0) {
        item it(ammo->id, 0);
        it.charges = amount;
        m->add_item( examx, examy, it );
    }

[sprawl15]

MormonPartyboat here. I did a bit more testing using the placed forge, and I found another quirk. There is no maximum for how much you can put into the forge - I was able to put ten million charcoal in at once.

Deconstruction seems to be WAI, it returns exactly as much charcoal as the forge thinks it contains.