[DRAFT] Support external references in derived tables

A motivating example of the CONNECT BY task includes a subquery with outer
references:

WHERE description LIKE :1

    AND type = ?

    AND status = ?

    AND EXISTS (

        SELECT ?

        FROM smt_group

        WHERE groupid = :2

        START WITH groupid = a.groupid

        CONNECT BY PRIOR parentid = groupid

    )

A problem with outer references comes from this:

• Recursive CTEs syntax uses derived tables
• The internal representation of Recursive CTEs also uses derived tables
• Derived tables currently do not have/support outer references

• If CONNECT BY is parsed into the same internal representation as Recursive CTEs, then we will need to internally support derived tables with outer references.

Attached is a patch by igor which adds support for outside references in the parser.

The execution part is not done yet, though. This task is about adding support for query execution.