pgsql: pg_plan_advice: Fix failures to accept identifier keywords.

pg_plan_advice: Fix failures to accept identifier keywords.

TOK_IDENT allows only non-keywords; identifier should be used
any place where either keywords or non-keywords should be accepted.
Hence, without this commit, any string that happens to be a keyword
can't be used as a partition schema, partition name, or plan name,
which is incorrect.

Author: Lukas Fittl <lukas(at)fittl(dot)com>
Discussion: http://postgr.es/m/CAP53PkzKeD=t90OfeMsniYrcRe2THQbUx3g6wV17Y=ZtiwmWTQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5e72ce2467c15340026955b57ff75f75e853a766

Modified Files
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contrib/pg_plan_advice/expected/syntax.out | 45 ++++++++++++++++++++++++++++++
contrib/pg_plan_advice/pgpa_parser.y | 6 ++--
contrib/pg_plan_advice/sql/syntax.sql | 19 +++++++++++++
3 files changed, 67 insertions(+), 3 deletions(-)