pgsql: Properly mention in the release notes that fillfactor controls

Log Message:
-----------
Properly mention in the release notes that fillfactor controls both heap
and indexes. Other cleanups.

Modified Files:
--------------
pgsql/doc/src/sgml:
release.sgml (r1.437 -> r1.438)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/release.sgml.diff?r1=1.437&r2=1.438)