pgsql: More regression test cases for json/jsonb extraction operators.

More regression test cases for json/jsonb extraction operators.

Cover some cases I omitted before, such as null and empty-string
elements in the path array. This exposes another inconsistency:
json_extract_path complains about empty path elements but
jsonb_extract_path does not.

Branch
------
REL9_4_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/9243417801be3f1cfaa3a3c33d5a003f382bd7a4

Modified Files
--------------
src/test/regress/expected/json.out | 62 ++++++++++++++++++++++++++++-
src/test/regress/expected/json_1.out | 62 ++++++++++++++++++++++++++++-
src/test/regress/expected/jsonb.out | 70 ++++++++++++++++++++++++++++++++-
src/test/regress/expected/jsonb_1.out | 70 ++++++++++++++++++++++++++++++++-
src/test/regress/sql/json.sql | 20 +++++++++-
src/test/regress/sql/jsonb.sql | 20 +++++++++-
6 files changed, 292 insertions(+), 12 deletions(-)