checkclnum
ret |= checkclnum(boot, no, cl, &fat[cl].next);
ret |= checkclnum(boot, no, cl, &fat[cl].next);
ret |= checkclnum(boot, no, cl, &fat[cl].next);
ret |= checkclnum(boot, no, cl, &fat[cl].next);
static int checkclnum(struct bootblock *, int, cl_t, cl_t *);