Move MYSQL_TIME initialization from Field_xxx::store_time_dec() to new constructors Time() and Datetime()

int Field_temporal_with_date::store_time_dec(const MYSQL_TIME *ltime, uint dec)

{

  int error= 0, have_smth_to_conv= 1;

  ErrConvTime str(ltime);

  MYSQL_TIME l_time;

  if (copy_or_convert_to_datetime(get_thd(), ltime, &l_time))

  {

    /*

      Set have_smth_to_conv and error in a way to have

      store_TIME_with_warning do bzero().

    */

    have_smth_to_conv= false;

    error= MYSQL_TIME_WARN_OUT_OF_RANGE;

  }

  else

  {

    /*

      We don't perform range checking here since values stored in TIME

      structure always fit into DATETIME range.

    */

    have_smth_to_conv= !check_date(&l_time, pack_time(&l_time) != 0,

                                   sql_mode_for_dates(get_thd()), &error);

  }

  return store_TIME_with_warning(&l_time, &str, error, have_smth_to_conv);

}

int Field_temporal_with_date::store_time_dec(const MYSQL_TIME *ltime, uint dec)

{

  int error;

  ErrConvTime str(ltime);

  THD *thd= get_thd();

  Datetime dt(thd, &error, ltime, sql_mode_for_dates(thd));

  ltime= dt.is_valid_datetime() ? dt.get_mysql_time() : NULL;

  return store_TIME_with_warning(const_cast<MYSQL_TIME*>(ltime), &str, error);

}