pgsql: Output timestamps in ISO 8601 format when rendering JSON.

Output timestamps in ISO 8601 format when rendering JSON.

Many JSON processors require timestamp strings in ISO 8601 format in
order to convert the strings. When converting a timestamp, with or
without timezone, to a JSON datum we therefore now use such a format
rather than the type's default text output, in functions such as
to_json().

This is a change in behaviour from 9.2 and 9.3, as noted in the release
notes.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/f30015b6d794c15d52abbb3df3a65081fbefb1ed

Modified Files
--------------
doc/src/sgml/release-9.4.sgml        |   18 +++++++++++++++
src/backend/utils/adt/json.c         |   41 ++++++++++++++++++++++++++++++++++
src/test/regress/expected/json.out   |   23 +++++++++++++++++++
src/test/regress/expected/json_1.out |   23 +++++++++++++++++++
src/test/regress/sql/json.sql        |   11 +++++++++
5 files changed, 116 insertions(+)