5218 posix definition of NULL
correct unistd.h and iso/stddef_iso.h
update gate source affected

*** 70,80 ****
                  return(FAIL);
          gsig=signal(SIGALRM, galarm);
          if (Debug > 4)
                  pkdebug = 1;
          Pk = pkopen(Ifn, Ofn);
!         if ((int) Pk == NULL)
                  return(FAIL);
          return(0);
  }
  
  int
--- 70,80 ----
                  return(FAIL);
          gsig=signal(SIGALRM, galarm);
          if (Debug > 4)
                  pkdebug = 1;
          Pk = pkopen(Ifn, Ofn);
!         if ( Pk == NULL)
                  return(FAIL);
          return(0);
  }
  
  int