Fail the query if the results were truncated

[Leonidas-from-XIV]

Closes #12.

[ygrek]

I believe this error is not for number of rows, but for the size of resulting columns.
See https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-fetch.html

MYSQL_DATA_TRUNCATED is returned when truncation reporting is enabled. To determine which column values were truncated when this value is returned, check the error members of the MYSQL_BIND structures used for fetching values. Truncation reporting is enabled by default, but can be controlled by calling mysql_options() with the MYSQL_REPORT_DATA_TRUNCATION option.

But now we cannot fail the query (because compatibility) but should introduce one more function or carry some flag?