Incorrect functions called to get error info when mysql_stmt_close fails

[smradCZ]

When mysql_stmt_close() fails the information about error should be obtained from mysql_error()/mysql_errno() calling instead of mysql_stmt_error()/mysql_stmt_errno().

The only occurrence in code base is located in include/superior_mysqlpp/low_level/dbdriver.hpp in method Statement::close().

See https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-close.html for more info.