pgsql: Fix more problems with rewriter failing to set Query.hasSubLinks

Log Message:
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Fix more problems with rewriter failing to set Query.hasSubLinks when inserting
a SubLink expression into a rule query.  We missed cases where the original
query contained a sub-SELECT in a function in FROM, a multi-row VALUES list,
or a RETURNING list.  Per bug #4434 from Dean Rasheed and subsequent
investigation.

Back-patch to 8.1; older releases don't have the issue because they didn't
try to be smart about setting hasSubLinks only when needed.

Tags:
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REL8_2_STABLE

Modified Files:
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    pgsql/src/backend/rewrite:
        rewriteHandler.c (r1.168.2.1 -> r1.168.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/rewrite/rewriteHandler.c?r1=1.168.2.1&r2=1.168.2.2)