serial datatype changes for v7.3?

Hi,

I'm playing around with the CVS version and noticed a change from 7.2 in
regards to serial datatypes - they no longer automatically have an
index. Is this a deliberate thing? I did a search in the archives but
didn't come across mention of the change. A pointer to discussion on
this would be great.

CREATE TABLE author (
authorid SERIAL,
firstname VARCHAR(255),
surname VARCHAR(255),
dateofbirth DATE,
gender CHAR(1)
);

NOTICE: CREATE TABLE will create implicit sequence
'author_authorid_seq' for SERIAL column 'author.authorid'
CREATE TABLE

library=# \d author
Table "public.author"
Column | Type | Modifiers
-------------+------------------------+--------------------------------------------------------------
authorid | integer | not null default
nextval('public.author_authorid_seq'::text)
firstname | character varying(255) |
surname | character varying(255) |
dateofbirth | date |
gender | character(1) |

library=# \di
No relations found.