pgsql: Fix the code that adds regclass constants to a plan's list of

Log Message:
-----------
Fix the code that adds regclass constants to a plan's list of relation OIDs
that it depends on for replan-forcing purposes. We need to consider plain OID
constants too, because eval_const_expressions folds a RelabelType atop a Const
to just a Const. This change could result in OID values that aren't really
for tables getting added to the dependency list, but the worst-case
consequence would be occasional useless replans. Per report from Gabriele
Messineo.

Modified Files:
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pgsql/src/backend/optimizer/plan:
setrefs.c (r1.141 -> r1.142)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/setrefs.c?r1=1.141&r2=1.142)