Add new JSON processing functions and parser API.

The JSON parser is converted into a recursive descent parser, and
exposed for use by other modules such as extensions. The API provides
hooks for all the significant parser event such as the beginning and end
of objects and arrays, and providing functions to handle these hooks
allows for fairly simple construction of a wide variety of JSON
processing functions. A set of new basic processing functions and
operators is also added, which use this API, including operations to
extract array elements, object fields, get the length of arrays and the
set of keys of a field, deconstruct an object into a set of key/value
pairs, and create records from JSON objects and arrays of objects.

Catalog version bumped.

Andrew Dunstan, with some documentation assistance from Merlin Moncure.

src/backend/catalog/system_views.sql

@@ -787,3 +787,11 @@ COMMENT ON FUNCTION ts_debug(text) IS
 CREATE OR REPLACE FUNCTION
   pg_start_backup(label text, fast boolean DEFAULT false)
   RETURNS text STRICT VOLATILE LANGUAGE internal AS 'pg_start_backup';
+
+CREATE OR REPLACE FUNCTION 
+  json_populate_record(base anyelement, from_json json, use_json_as_text boolean DEFAULT false)
+  RETURNS anyelement LANGUAGE internal STABLE AS 'json_populate_record';
+
+CREATE OR REPLACE FUNCTION 
+  json_populate_recordset(base anyelement, from_json json, use_json_as_text boolean DEFAULT false)
+  RETURNS SETOF anyelement LANGUAGE internal STABLE ROWS 100  AS 'json_populate_recordset';

src/backend/utils/adt/Makefile

@@ -19,8 +19,8 @@ OBJS = acl.o arrayfuncs.o array_selfuncs.o array_typanalyze.o \
 	array_userfuncs.o arrayutils.o bool.o \
 	cash.o char.o date.o datetime.o datum.o domains.o \
 	enum.o float.o format_type.o \
-	geo_ops.o geo_selfuncs.o int.o int8.o json.o like.o lockfuncs.o \
-	misc.o nabstime.o name.o numeric.o numutils.o \
+	geo_ops.o geo_selfuncs.o int.o int8.o json.o jsonfuncs.o like.o \
+	lockfuncs.o misc.o nabstime.o name.o numeric.o numutils.o \
 	oid.o oracle_compat.o pseudotypes.o rangetypes.o rangetypes_gist.o \
 	rowtypes.o regexp.o regproc.o ruleutils.o selfuncs.o \
 	tid.o timestamp.o varbit.o varchar.o varlena.o version.o xid.o \