pgsql: Remove ruleutils.c's use of varnoold/varoattno as a shortcut for

Log Message:
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Remove ruleutils.c's use of varnoold/varoattno as a shortcut for determining
what a Var node refers to. This is no longer necessary because the new
flat-range-table representation of plan trees makes it relatively easy to dig
down through child plan levels to find the original reference; and to keep
doing it that way, we'd have to store joinaliasvars lists in flattened RTEs,
as demonstrated by bug report from Leszek Trenkner. This change makes
varnoold/varoattno truly just debug aids, which wasn't quite the case before.
Perhaps we should drop them, or only have them in assert-enabled builds?

Modified Files:
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pgsql/src/backend/utils/adt:
ruleutils.c (r1.257 -> r1.258)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c.diff?r1=1.257&r2=1.258)