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:
--------------
    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)