pgsql: Fix YA unwanted behavioral difference with operator_precedence_w

Fix YA unwanted behavioral difference with operator_precedence_warning.

Jeff Janes noted that the error cursor position shown for some errors
would vary when operator_precedence_warning is turned on. We'd prefer
that option to have no undocumented effects, so this isn't desirable.
To fix, make sure that an AEXPR_PAREN node has the same exprLocation
as its child node.

(Note: it would be a little cheaper to use @2 here instead of an
exprLocation call, but there are cases where that wouldn't produce
the identical answer, so don't do it like that.)

Back-patch to 9.5 where this feature was introduced.

Discussion: https://postgr.es/m/CAMkU=1ykK+VhhcQ4Ky8KBo9FoaUJH3f3rDQB8TkTXi-ZsBRUkQ@mail.gmail.com

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/2b47e29f2081f7b2bbe99d240bdd08f63438357e

Modified Files
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src/backend/parser/gram.y | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)