Make item upgrades have an adaptive sprite

[Dinopony]

By editing the global section from DATAS.BIN loaded on boot inside the RAM, we can dynamically change the sprite of an item. It would be interesting to incorporate inside func_alter_item_id instructions setting the sprite pointer value for that item upgrade.

It would basically do the same iterative process to find tier+2 instead of tier+1, and set the sprite for that item upgrade to this new item's sprite.

[Dinopony]

As suggested by Spiriax, it would also be cool to have the corresponding item name being displayed instead of having "X upgrade" displayed.