New functions to handle date-only formats:
- native date(out[], out_len = sizeof(out));
- native datetime_to_date(datetime[], out[], out_len = sizeof(out));
- native date_to_datetime(date[], out[], out_len = sizeof(out));
- native date_to_timestamp(date[]);
- native timestamp_to_date(timestamp, out[], out_len = sizeof(out));