wn_printf -- window printf

        USAGE

          wn_printf(wn, cs, args)
          WINDOWPTR wn;
          char *cs;
          ?? arg1 ... argn;

                wn   - window handle
                cs   - format control string
                args - argument list

          printf function for windows!

        RETURNS

          TRUE or NULL if error

        CAUTIONS

          Output string length is limited to 254 bytes.
          Registered users can, of course, edit the wn_printf function
          set the limit to whatever they wish.

          Integer only for Microsoft 3.0.  This limitation
          be overcome by using sprintf in conjunction with wn_printf.
          For example:

                  char buf[256];
                       ..
                       ..
                  sprintf(buf,"%d %l %x\n", intval, longval, hexval);
                  wn_printf(wn, buf);

          Full support in Microsoft 4.0, Lattice, CI86, and Datalight.

          The window "wn" automatically becomes the top window tile upon
          return.