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_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/4f33572ee68b515dc2750e265fc0d0312c0d5d3d

Modified Files
--------------
src/backend/utils/adt/date.c       |    3 +--
src/backend/utils/adt/json.c       |   36 ++++++++++--------------------------
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/sql/json.sql      |    3 +++
7 files changed, 35 insertions(+), 30 deletions(-)