rename index fields bug

I've just stumbled across this, which appears to be a regression from
8.4 that is present in 9.0 and master:

andrew=# create table foo (x int primary key);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
"foo_pkey" for table "foo"
CREATE TABLE
andrew=# alter table foo rename x to y;
ALTER TABLE
andrew=# select attname from pg_attribute where attrelid =
'foo_pkey'::regclass;
attname
---------
x
(1 row)

In 8.4 the index attribute is renamed correctly.

This only came to light because it caused a londiste failure, making
londiste think that there wasn't a key field. Arguably londiste should
be using pg_index.indkey, but this should still work right.

cheers

andrew