fix for mysql

[sheercat]

at dialect_mysql.go

func (this MysqlDialect) ListColumns(dbname string, table Table) string {
return fmt.Sprintf(select column_name, data_type from information_schema.columns where table_schema = 'main' and table_name='%s', table.Name)
}

is maybe

func (this MysqlDialect) ListColumns(dbname string, table Table) string {
return fmt.Sprintf(select column_name, data_type from information_schema.columns where table_schema = '%s' and table_name='%s', dbname, table.Name)
}

Thank you.