Add a bunch of pseudo-types to replace the behavior formerly associated

with OPAQUE, as per recent pghackers discussion.  I still want to do some
more work on the 'cstring' pseudo-type, but I'm going to commit the bulk
of the changes now before the tree starts shifting under me ...

contrib/rserv/master.sql.in

@@ -79,7 +79,7 @@ create sequence _rserv_sync_seq_;
 drop function _rserv_log_();
 
 CREATE FUNCTION _rserv_log_()
-	RETURNS opaque
+	RETURNS trigger
 	AS '@MODULE_FILENAME@'
 	LANGUAGE 'c'
 ;