pgsql: Mention configurations early in text search documentation to

Log Message:
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Mention configurations early in text search documentation to table/index
section makes a little more sense.

Modified Files:
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pgsql/doc/src/sgml:
textsearch.sgml (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/textsearch.sgml?r1=1.3&r2=1.4)