pgsql: Fix incorrect tlist generation in create_gather_plan().

Fix incorrect tlist generation in create_gather_plan().

This function is written as though Gather doesn't project; but it does.
Even if it did not project, though, we must use build_path_tlist to ensure
that the output columns receive correct sortgroupref labeling.

Per report from Amit Kapila.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/8776c15c85322612b9bf79daf50f74be71c12e05

Modified Files
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src/backend/optimizer/plan/createplan.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)