CloseWD
CloseWD Close and release a working directory
#include <Files.h> File Manager (PBxxx)
OSErr CloseWD(wdRefNum );
short wdRefNum ; id of open working directory to be closed
returns Error Code; 0=no error
CloseWD closes a working directory.
Returns: an operating system Error Code. It will be one of:
noErr (0) No error
nsvErr (-35) No such volume

Notes: You should only call CloseWD or PBCloseWD on working directories you
have created. Do not call CloseWD or PBCloseWD on working directories
created by Standard File or SysEnvirons.