Convert (most) old-style classes in Util.py to new-style classes.  Refactor assignment to Util.DisplayEngine.__call__.  Update __new__() use in Util.Null.  Proxy is still unconverted.
Convert (most) old-style classes in Util.py to new-style classes.  Refactor assignment to Util.DisplayEngine.__call__.  Update __new__() use in Util.Null.  Proxy is still unconverted.

Distrotech/scons,Distrotech/scons,Distrotech/scons,Distrotech/scons,Distrotech/scons