Log Message:
-----------
Update xindex.sgml to discuss operator families.
Modified Files:
--------------
pgsql/doc/src/sgml:
xindex.sgml (r1.55 -> r1.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xindex.sgml.diff?r1=1.55&r2=1.56)