pgsql: Fix recursion into previously planned sub-query in examine_simpl

Fix recursion into previously planned sub-query in examine_simple_variable.

This code was looking at the sub-Query tree as seen in the parent query's
RangeTblEntry; but that's the pristine parser output, and what we need to
look at is the tree as it stands at the completion of planning.  Otherwise
we might pick up a Var that references a subquery that got flattened and
hence has no RelOptInfo in the subroot.  Per report from Peter Geoghegan.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/79edb2b1dc33166b576f51a8255a7614f748d9c9

Modified Files
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src/backend/utils/adt/selfuncs.c |   11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)