Support object tables

[Андрей Турбанов]

Example

CREATE TYPE obj_type1 AS object(
attr varchar2(1)
);
/


CREATE TYPE obj_type2 AS object(
attr varchar2(3),
obj1 obj_type1
);
/

CREATE TYPE obj_type3 AS object(
attr varchar2(4),
obj2 obj_type2
);
/

CREATE TABLE objtest OF obj_type3;