Legacy: Destroyed staves

[Froof]

Staves release all their stored charges when destroyed. If a monster destroys a staff in your inventory, it should release all the charges it had, be it good or bad. If it's a staff of destruction, and it's got 4 charges left, it destructs 4 times. If it's a staff of teleport with 8 left, you bounce around 8 times before it goes *poof*.