Expand enemy gold drops to use 3 bytes rather than 2

[Taeveril]

Enemy gold drops cap at 65535 (0xFFFF). With enemy groups adding a 10% bonus, hitting this cap can happen frequently in the randomizer.

Party gold caps at 999,999; meaning that value is already saved/stored with 3 bytes.

It makes logistical sense for enemy gold drops to also use 3 bytes.