pgsql: Add description of new features

Log Message:
-----------
Add description of new features

Modified Files:
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    pgsql/contrib/tsearch2/docs:
        tsearch-V2-intro.html (r1.7 -> r1.8)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/docs/tsearch-V2-intro.html.diff?r1=1.7&r2=1.8)
        tsearch2-guide.html (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/docs/tsearch2-guide.html.diff?r1=1.2&r2=1.3)
        tsearch2-ref.html (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/docs/tsearch2-ref.html.diff?r1=1.4&r2=1.5)