pgsql: Prevent planner from including temp tables of other backends when

Log Message:
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Prevent planner from including temp tables of other backends when expanding
an inheritance tree. Per recent discussions.

Modified Files:
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pgsql/src/backend/optimizer/prep:
prepunion.c (r1.125 -> r1.126)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/prep/prepunion.c.diff?r1=1.125&r2=1.126)