Log Message:
-----------
Update interval documenation to mention the storage system used.
Modified Files:
--------------
pgsql/doc/src/sgml:
datatype.sgml (r1.163 -> r1.164)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml.diff?r1=1.163&r2=1.164)