Prevent a rowtype from being included in itself via a range.

We probably should have thought of this case when ranges were added,
but we didn't.  (It's not the fault of commit eb51af71f, because
ranges didn't exist then.)

It's an old bug, so back-patch to all supported branches.

Discussion: https://postgr.es/m/7782.1577051475@sss.pgh.pa.us

src/test/regress/expected/rangetypes.out

@@ -1375,6 +1375,9 @@ select *, row_to_json(upper(t)) as u from
  ["(5,6)","(7,8)") | {"a":7,"b":8}
 (2 rows)
 
+-- this must be rejected to avoid self-inclusion issues:
+alter type two_ints add attribute c two_ints_range;
+ERROR:  composite type two_ints cannot be made a member of itself
 drop type two_ints cascade;
 NOTICE:  drop cascades to type two_ints_range
 --

src/test/regress/sql/rangetypes.sql

@@ -463,6 +463,9 @@ select *, row_to_json(upper(t)) as u from
   (values (two_ints_range(row(1,2), row(3,4))),
           (two_ints_range(row(5,6), row(7,8)))) v(t);
 
+-- this must be rejected to avoid self-inclusion issues:
+alter type two_ints add attribute c two_ints_range;
+
 drop type two_ints cascade;
 
 --