When materialized views were added, psql's \d commands were made to
treat them as a separate object category ... but not everyplace in the
documentation or comments got the memo.

Noted by David Johnston.  Back-patch to 9.3 where matviews came in.

Discussion: https://postgr.es/m/CAKFQuwb27M3VXRhHErjCpkWwN9eKThbqWb1=trtoXi9_ejqPXQ@mail.gmail.com