Revert "(CodeThorn) Project uses ROSE WorkList rather than its own impl."

This reverts commit 9589d26b2b8f1f9bd774a516fd5269f57cd54af7 so as not
to touch Markus's baby. ;-)

The next commit will change the name of ROSE's WorkList.h so as not to conflict
with the CodeThorn project's WorkList.h.
(Support) Renamed ROSE's WorkList.h to WorkLists.h