Add pg_buffercache contrib module, from Mark Kirkwood.

contrib/pg_buffercache/pg_buffercache.sql.in

@@ -0,0 +1,18 @@
+-- Adjust this setting to control where the objects get created.
+SET search_path = public;
+
+-- Register the function.
+CREATE OR REPLACE FUNCTION pg_buffercache_pages()
+RETURNS SETOF RECORD
+AS 'MODULE_PATHNAME', 'pg_buffercache_pages'
+LANGUAGE 'C';
+
+-- Create a view for convenient access.
+CREATE VIEW pg_buffercache AS
+	SELECT P.* FROM pg_buffercache_pages() AS P
+ 	(bufferid integer, relfilenode oid, reltablespace oid, reldatabase oid, 
+ 	 relblocknumber numeric(10), isdirty bool);
+ 
+-- Don't want these to be available at public.
+REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
+REVOKE ALL ON pg_buffercache FROM PUBLIC;