Bug in pg_describe_object (was: Re: [HACKERS] obj_unique_identifier(oid))

Here is the bug-fix patch again with a description of the context so I
can add it to the commit fest.

Joel Jacobson discovered a bug in the function pg_describe_object where
it does not produce unique identifiers for some entries in pg_amproc.

This patch fixes the bug where when two entries in pg_amproc only differ
in amproclefttype or amprocrighttype the same description will be
produced by pg_describe_object, by simply adding the two fields
(amproclefttype, amprocrighttype) to the description.

== Before patch

SELECT pg_describe_object('pg_amproc'::regclass,oid,0)
FROM pg_amproc WHERE oid IN (10608,10612);
pg_describe_object
------------------------------------------------------------------------------------
function 1 bttextcmp(text,text) of operator family array_ops for access method gin
function 1 bttextcmp(text,text) of operator family array_ops for access method gin
(2 rows)

== After patch

SELECT pg_describe_object('pg_amproc'::regclass,oid,0)
FROM pg_amproc WHERE oid IN (10608,10612);
pg_describe_object
----------------------------------------------------------------------------------------------------------------------------------
function 1 bttextcmp(text,text) of operator family array_ops for access method gin for (text[],text[])
function 1 bttextcmp(text,text) of operator family array_ops for access method gin for (character varying[],character varying[])
(2 rows)

Regards,
Andreas