Generate Oracle ROWNUM scheme using named subqueries

Generate Oracle ROWNUM scheme using named subqueries

The LIMIT / OFFSET scheme used in Oracle now makes use of named subqueries
rather than unnamed subqueries when it transparently rewrites a SELECT
statement to one that uses a subquery that includes ROWNUM.  The change is
part of a larger change where unnamed subqueries are no longer directly
supported by Core, as well as to modernize the internal use of the select()
construct within the Oracle dialect.

Change-Id: I27605d7cf16ce79f9d577dbc84e3bd51b7c9b4ae