Starting with Version 9.1, PostgreSQL provides a convenient way to move from the primordial ooze of unversioned contrib modules into the brave new world of extensions. Basically, you provide a SQL file to show the relationship of the objects to the extension. The contrib module's cube provides a good example of this in cube--unpackaged--1.0.sql:

/* contrib/cube/cube--unpackaged--1.0.sql */

-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION cube" to load this file. \quit

ALTER EXTENSION cube ADD type cube;
ALTER EXTENSION cube ADD function cube_in(cstring);
ALTER EXTENSION cube ADD function cube(double precision[],double precision[]);
ALTER EXTENSION cube ADD function cube(double precision[]);
...

The code that provides multidimensional cubes for PostgreSQL has been stable for quite some time. It is unlikely that a new version will be created any time soon. The only reason for this module to be converted into an extension...