pgsql: Fix incorrect translation of minus-infinity datetimes for json/j

Fix incorrect translation of minus-infinity datetimes for json/jsonb.

Commit bda76c1c8cfb1d11751ba6be88f0242850481733 caused both plus and
minus infinity to be rendered as "infinity", which is not only wrong
but inconsistent with the pre-9.4 behavior of to_json().  Fix that by
duplicating the coding in date_out/timestamp_out/timestamptz_out more
closely.  Per bug #13687 from Stepan Perlov.  Back-patch to 9.4, like
the previous commit.

In passing, also re-pgindent json.c, since it had gotten a bit messed up by
recent patches (and I was already annoyed by indentation-related problems
in back-patching this fix ...)

Branch
------
REL9_5_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/5fb20a5ba6ce963ad529224ff5359aa1731c4068

Modified Files
--------------
src/backend/utils/adt/date.c        |    3 +-
src/backend/utils/adt/json.c        |   72 ++++++++++++++---------------------
src/backend/utils/adt/jsonb.c       |   54 ++++++++------------------
src/backend/utils/adt/timestamp.c   |    3 +-
src/include/utils/date.h            |    1 +
src/include/utils/datetime.h        |    1 +
src/test/regress/expected/json.out  |   18 +++++++++
src/test/regress/expected/jsonb.out |   18 +++++++++
src/test/regress/sql/json.sql       |    3 ++
src/test/regress/sql/jsonb.sql      |    3 ++
10 files changed, 90 insertions(+), 86 deletions(-)