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/fulltextindex/fti.c

@@ -21,7 +21,7 @@
  *	Example:
  *
  *	-- Create the SQL function based on the compiled shared object
- *	create function fti() returns opaque as
+ *	create function fti() returns trigger as
  *	  '/usr/local/pgsql/lib/contrib/fti.so' language 'C';
  *
  *	-- Create the FTI table