Log Message:
-----------
Document how *_blks_read statistics columns are computed.
Modified Files:
--------------
pgsql/doc/src/sgml:
monitoring.sgml (r1.67 -> r1.68)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml?r1=1.67&r2=1.68)