Add CINE for ALTER TABLE ... ADD COLUMN

Hi all,

This simple patch add CINE for ALTER TABLE ... ADD COLUMN.

So now we can:

ALTER TABLE foo
ADD COLUMN IF NOT EXISTS c1 integer;

and/or ...

ALTER TABLE foo
ADD COLUMN IF NOT EXISTS c1 integer,
ADD COLUMN c2 integer;

Regards,

--
Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
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