SQL to display user functions

I'm the author of phpPgAdmin and just discovered a bug in my app.

I use the following query to get the user defined functions:

SELECT
  proname,
  pt.typname AS result,
  oidvectortypes(pc.proargtypes) AS arguments
FROM
  pg_proc pc, pg_user pu, pg_type pt
WHERE
  pc.proowner = pu.usesysid
  AND pc.prorettype = pt.oid
  AND pc.oid > '<max system oid>'::oid

I just realized that this does not retrieve functions with the return
datatype of OPAQUE because it is not a registered datatype. The prorettype =
0 when the function's return type is created as OPAQUE rather than the oid
of a "real" datatype.  I know I could do an outer join, but they are not yet
fully implemented.

What would be the most graceful way to handle this?

Tom, you helped me with my last kludgy query to get the indicies... can you
help here?

Thanks,

-Dan

PS. I'm pretty sure this is a bug in psql as well.  I tried a \df
update_pg_pwd (which is a system function that has a rettype of OPAQUE [or
at least 0]) and it return anything.