pgsql: Improve wordings by David Fuhry

Log Message:
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Improve wordings by David Fuhry <dfuhry@cs.kent.edu>

Modified Files:
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    pgsql/doc/src/sgml:
        config.sgml (r1.87 -> r1.88)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml.diff?r1=1.87&r2=1.88)
        gin.sgml (r2.3 -> r2.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/gin.sgml.diff?r1=2.3&r2=2.4)
        indices.sgml (r1.63 -> r1.64)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/indices.sgml.diff?r1=1.63&r2=1.64)
        mvcc.sgml (r2.61 -> r2.62)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/mvcc.sgml.diff?r1=2.61&r2=2.62)
        xindex.sgml (r1.48 -> r1.49)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xindex.sgml.diff?r1=1.48&r2=1.49)