alter table ad primary key

Hello,

trying "alter table buecher add primary key (isbn);"
gives the error "ALTER TABLE / ADD CONSTRAINT is not implemented"
with PG 7.1.

Does anybody know whether this works with a newer PG version?

Did someone already implement a workaround in form of a stored
procedure that does the following:
  - copy the table entirely to a temporary table
  - remember all indices, constraints, rules and triggers on the old table
    (is that possible at all?)
  - drop the old table
  - recreate the table with a primary key
  - copy the temp table bakc
  - drop the temp table
?

Thanks,

Christoph Dalitz