pgsql: Make an editorial pass over the newly SGML-ified contrib

Log Message:
-----------
Make an editorial pass over the newly SGML-ified contrib documentation.
Fix lots of bad markup, bad English, bad explanations.

Second round of commits. pgcrypto and pgstandby still to go...

Modified Files:
--------------
pgsql/doc/src/sgml:
intagg.sgml (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/intagg.sgml?r1=1.2&r2=1.3)
intarray.sgml (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/intarray.sgml?r1=1.4&r2=1.5)
isn.sgml (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/isn.sgml?r1=1.3&r2=1.4)
ltree.sgml (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ltree.sgml?r1=1.2&r2=1.3)
oid2name.sgml (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/oid2name.sgml?r1=1.2&r2=1.3)
pageinspect.sgml (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pageinspect.sgml?r1=1.2&r2=1.3)
pgbench.sgml (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgbench.sgml?r1=1.3&r2=1.4)
pgbuffercache.sgml (r2.1 -> r2.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgbuffercache.sgml?r1=2.1&r2=2.2)
pgfreespacemap.sgml (r2.1 -> r2.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgfreespacemap.sgml?r1=2.1&r2=2.2)
pgrowlocks.sgml (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgrowlocks.sgml?r1=1.3&r2=1.4)
pgstattuple.sgml (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgstattuple.sgml?r1=1.2&r2=1.3)
pgtrgm.sgml (r2.1 -> r2.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgtrgm.sgml?r1=2.1&r2=2.2)