Went back to using "staffs{ as the plural of staff rather than "staves" since saw...

Went back to using "staffs{ as the plural of staff rather than "staves" since saw some sources indicating that both are acceptable and some treating "staves" as archaic. Using "staves" as the plural also would require some modification of object_desc() and the k_info.txt entries for "Quarterstaff", "Jo Staff", and "Bo Staff".