pgsql: Improve reporting for syntax errors in multi-line JSON data.

Improve reporting for syntax errors in multi-line JSON data.

Point to the specific line where the error was detected; the
previous code tended to include several preceding lines as well.
Avoid re-scanning the entire input to recompute which line that
was. Simplify the logic a bit. Add test cases.

Simon Riggs and Hamid Akhtar, reviewed by Daniel Gustafsson and myself

Discussion: https://postgr.es/m/CANbhV-EPBnXm3MF_TTWBwwqgn1a1Ghmep9VHfqmNBQ8BT0f+_g@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ffd3944ab9d481906137bc7d20f5325a2bd68acc

Modified Files
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src/backend/utils/adt/jsonfuncs.c | 23 ++++++-----------------
src/common/jsonapi.c | 8 +++++---
src/include/common/jsonapi.h | 4 ++--
src/test/regress/expected/json.out | 35 +++++++++++++++++++++++++++++++++++
src/test/regress/expected/jsonb.out | 31 +++++++++++++++++++++++++++++++
src/test/regress/sql/json.sql | 17 +++++++++++++++++
src/test/regress/sql/jsonb.sql | 17 +++++++++++++++++
7 files changed, 113 insertions(+), 22 deletions(-)