pgsql: Fix json_to_record() bug with nested objects.

Fix json_to_record() bug with nested objects.

A thinko concerning nesting depth caused json_to_record() to produce bogus
output if a field of its input object contained a sub-object with a field
name matching one of the requested output column names. Per bug #13996
from Johann Visagie.

I added a regression test case based on his example, plus parallel tests
for json_to_recordset, jsonb_to_record, jsonb_to_recordset. The latter
three do not exhibit the same bug (which suggests that we may be missing
some opportunities to share code...) but testing seems like a good idea
in any case.

Back-patch to 9.4 where these functions were introduced.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/a9d199f6d3b998929cdb8e8aa61e5cd8db9b220f

Modified Files
--------------
src/backend/utils/adt/jsonfuncs.c | 2 +-
src/test/regress/expected/json.out | 16 ++++++++++++++++
src/test/regress/expected/jsonb.out | 16 ++++++++++++++++
src/test/regress/sql/json.sql | 7 +++++++
src/test/regress/sql/jsonb.sql | 8 ++++++++
5 files changed, 48 insertions(+), 1 deletion(-)