The ALTER TABLE syntax that you mention works at 8.1.6 also.

Depending on the problem, it is sometimes adequate just to add freelists, but in general it is best to rebuild the table as well.

On your website I think you mentioned that for changing the freelists of a table we have to rebuild the table, but in 8.1.7. it's possible to add freelists without rebuilding the table.

    alter table xx storage (freelists 13);