Add support for data change delta tables

Hello all,

Currently PostgreSQL doesn't support data change delta tables. For example, it doesn't support this type of query:

SELECT * FROM NEW TABLE (
     INSERT INTO phone_book
     VALUES ( 'Peter Doe', '555-2323' )
) AS t

PostgreSQL has RETURNING that provides only a subset of this functionality.

So I suggest to add support for data change delta tables. Because this feature is more powerful and it is included
in the SQL Standard.

Best regards, Pavel