NAME
       CD_PROTSTATUS -- return whether the current disk is write-protected.

   FUNCTION
       This command is used to determine whether the current disk is
       write-protected.  Currently, this function always returns write-
       protected status.  If write-once CDs are made available at some point,
       this may change.

   IO REQUEST INPUT
       io_Device       preset by the call to opendevice()
       io_Unit         preset by the call to opendevice()
       io_Command      CD_PROTSTATUS

   IO REQUEST RESULT
       io_Error - 0 for success, or an error code as defined in
                  <devices/cd.h>
       io_Actual - 0 means the disk is NOT write-protected, while any other
                   value indicates it is.