PostgreSQL 8.3's equivalent for Oracle's ROWNUM?

Question

In Oracle you can do:

select 
    rownum, -- here's the magic
    name as country, 
    population as pop_mil
from 
    country 
where 
    name like 'C%' and
    member = true
order by 
    population;

and get

rownum  country   pop_mil
------  --------  -------
     1  Croatia         5
     2  Chad           11
     3  Cuba           11
     4  Canada         35
     5  Colombia       48
     6  China        1360

Note that rownum has no relation to how rows are stored in the table. It's a pseudocolumn that enumerates the rows in the resulset after all filters and sort operations are done.

I know there's a workaround (row_number() over ...) in versions >= 8.4 (here), but my database is 8.3 and ther're no plans of migrating anytime soon.

- Is there a way to do that in PostgreSQL 8.3 ?