function cleanupCache(statement) {
	if (!statement) {
		return;
	}
	if (!alasql.options.cache) {
		return;
	}
	// cleanup the table data to prevent storing this information in the SQL cache
	if (statement && statement.query && statement.query.data) {
		statement.query.data = [];
	}
}
Clears any unneeded properties from a given AST statement closure used for caching
@param {Object} statement the statement to cleanup