Foreign key to column on same table at table creation time

I've noticed (at least in pgAdmin III v1.8.4) that I can't create a foreign
key constraint pointing to the table I'm in the process of creating. I can
do it manually though. Here's an example:
CREATE TABLE testtable
(
id serial NOT NULL,
parent_id integer,
CONSTRAINT pk_testtable_id PRIMARY KEY (id),
CONSTRAINT fk_testtable_parent_id FOREIGN KEY (parent_id)
REFERENCES testtable (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION
)

I could achieve this if I create the table then apply the foreign key, but
it would be nice to be able to do this one step. Is it possible to add this
for a future release?

Thanks

Thom