Log Message:
-----------
Support functions for index opclasses should be immutable.
Found by running opr_sanity on contrib modules.
Modified Files:
--------------
pgsql/contrib/cube:
cube.sql.in (r1.20 -> r1.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/cube/cube.sql.in?r1=1.20&r2=1.21)