Item prototypes use unique codes to keep them differentiated.  This is important for savefiles
since items may change between game versions.  The savefile stores the unique code and attempts to
restore the item to the inventory from the code.

If a code is deprecated, mark it as such.

Numbers below 1 are invalid.  0 is invalid as it's a system code, negatives are invalid as the file
saves unsigned integers.

Code - Item
   1 - Sweet Apple
   2 - Healing Poultice
   3 - Smelling Salts
   4 - Anti-Venom
   5 - Delicious Fungus

 100 - Inventor's Friend:  Volume 51

 200 - Unused
 201 - Iron Horseshoes
 202 - Heavy Iron Horseshoes
 203 - Adventurer's Straw Hat
 204 - Royal Student's Robes
 205 - Woven Wool Cloak
 
 300 - Applejack's Hat

(Quest Items)
5000 - Box of Muffins