pgsql: Revert 95d737ff to add 'ignore_nulls'

Revert 95d737ff to add 'ignore_nulls'

Per discussion, revert the commit which added 'ignore_nulls' to
row_to_json.  This capability would be better added as an independent
function rather than being bolted on to row_to_json.  Additionally,
the implementation didn't address complex JSON objects, and so was
incomplete anyway.

Pointed out by Tom and discussed with Andrew and Robert.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c8a026e4f15e2063cd7fe6cb9ffe44f2a81398bd

Modified Files
--------------
doc/src/sgml/func.sgml               |    6 ++--
src/backend/catalog/system_views.sql |   14 --------
src/backend/utils/adt/json.c         |   55 +++++++++++++++++++++++---------
src/include/catalog/catversion.h     |    2 +-
src/include/catalog/pg_proc.h        |    8 +++--
src/include/utils/json.h             |    2 ++
src/test/regress/expected/json.out   |   58 ----------------------------------
src/test/regress/sql/json.sql        |   24 --------------
8 files changed, 51 insertions(+), 118 deletions(-)