I doubt Stefan added the keycodes...they are those used by the BIOS/Windows. Just look in some table for the keycodes for the arrow keys.
Here, I found those in the header file of a DOS game programming library (Allegro):
NPC Code:
#define KEY_LEFT 82
#define KEY_RIGHT 83
#define KEY_UP 84
#define KEY_DOWN 85
I didn't test them though.