BUG #1010: format_type errors oin formatting type interval.

The following bug has been logged online:

Bug reference:      1010
Logged by:          Jeff Davis
Email address:      pg@xarg.net
PostgreSQL version: 7.4
Operating system:   Linux, Mac OS X 10.3
Description:        format_type errors oin formatting type interval.
Details:

head=# select version();
version
--------------------------------------------------------
 PostgreSQL 7.4 on powerpc-apple-darwin7.0.0, compiled by GCC gcc (GCC) 3.3 20030304 (Apple Computer, Inc. build 1495)

head=# select pg_catalog.format_type(oid, typlen) from pg_type where typname = 'interval';
ERROR:  invalid INTERVAL typmod: 0xc

Same error on linux.  Does not happen on 7.3.4.