BUG #6172: DROP EXTENSION error without CASCADE

The following bug has been logged online:

Bug reference:      6172
Logged by:          Hitoshi Harada
Email address:      umi.tanuki@gmail.com
PostgreSQL version: 9.1RC1
Operating system:   Windows7
Description:        DROP EXTENSION error without CASCADE
Details:

On pure-installed RC1 database, you can CREATE EXTENSION, but cannot DROP
it.

CREATE EXTENSION cube;
DROP EXTENSION cube;

ERROR:  cannot drop extension cube because other objects depend on it
DETAIL:  operator <>(cube,cube) depends on function cube_ne(cube,cube)
operator >(cube,cube) depends on function cube_gt(cube,cube)
operator <=(cube,cube) depends on function cube_le(cube,cube)
operator >=(cube,cube) depends on function cube_ge(cube,cube)
operator <@(cube,cube) depends on function cube_contained(cube,cube)
operator ~(cube,cube) depends on function cube_contained(cube,cube)
HINT:  Use DROP ... CASCADE to drop the dependent objects too.

DROP EXTENSION ... CASCADE; works but without CASCADE should work as source
build on Linux does it.