fix warning about overflow if matiec is running on 64-bit platform,
but the generated C code will cross-compiled for 32-bit platform

For example:
./build/config.c:29:39: error: large integer implicitly truncated to unsigned type [-Werror=overflow]
unsigned long greatest_tick_count__ = 18446744073709551611UL; /*tick*/
^
compilation terminated due to -Wfatal-errors.
cc1: all warnings being treated as errors

FUNCTION WEIGH : WORD     (* BCD encoded *)
  VAR_INPUT  (* "EN" input is used to indicate "scale ready" *)
    weigh_command : BOOL;
    gross_weight : WORD ; (* BCD encoded *)
    tare_weight : INT ;
  END_VAR
(* Function Body *)
IF weigh_command THEN
  WEIGH := INT_TO_BCD (BCD_TO_INT(gross_weight) - tare_weight);
END_IF ;

END_FUNCTION                     (* Implicit "ENO" *)