pgsql: JSON generation improvements.

JSON generation improvements.

This adds the following:

    json_agg(anyrecord) -> json
    to_json(any) -> json
    hstore_to_json(hstore) -> json (also used as a cast)
    hstore_to_json_loose(hstore) -> json

The last provides heuristic treatment of numbers and booleans.

Also, in json generation, if any non-builtin type has a cast to json,
that function is used instead of the type's output function.

Andrew Dunstan, reviewed by Steve Singer.

Catalog version bumped.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/38fb4d978c5bfc377ef979e2595e3472744a3b05

Modified Files
--------------
contrib/hstore/expected/hstore.out |   36 ++++
contrib/hstore/hstore--1.1.sql     |   13 ++
contrib/hstore/hstore_io.c         |  217 ++++++++++++++++++++++++
contrib/hstore/sql/hstore.sql      |   12 ++
doc/src/sgml/func.sgml             |   48 ++++++
doc/src/sgml/hstore.sgml           |   23 +++
src/backend/utils/adt/json.c       |  317 +++++++++++++++++++++++++++++++++---
src/include/catalog/catversion.h   |    2 +-
src/include/catalog/pg_aggregate.h |    3 +
src/include/catalog/pg_proc.h      |    8 +
src/include/utils/json.h           |    5 +
src/test/regress/expected/json.out |   24 +++
src/test/regress/sql/json.sql      |   12 ++
13 files changed, 699 insertions(+), 21 deletions(-)