134d3e8d7e
This used to be done, but pulled in tables which slowed down connections on databases with a large number of tables; see https://github.com/jackc/pgx/issues/140. This change includes composite types but excludes tables by joining against [pg_class](https://www.postgresql.org/docs/11/catalog-pg-class.html) in which `relkind` is `'c'` for the former and `'r'` for the latter. Fixes https://github.com/jackc/pgx/issues/420.