pgsql: Reduce the permissions check needed to use pgrowlocks() to having

Log Message:
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Reduce the permissions check needed to use pgrowlocks() to having
SELECT on the target table. Per discussion.

Modified Files:
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pgsql/contrib/pgrowlocks:
pgrowlocks.c (r1.6 -> r1.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgrowlocks/pgrowlocks.c?r1=1.6&r2=1.7)