cleanup: avoid passing parameters to object.__new__
cleanup: avoid passing parameters to object.__new__

In Python3 this invocation is an error in the case where the superclass
is object.  The parameters might still be interpreted by non-object
superclasses, so we need a conditional.

See: http://stackoverflow.com/questions/19718062/determine-whether-super-new-will-be-object-new-in-python-3

pabigot/pyxb,pabigot/pyxb,CantemoInternal/pyxb,CantemoInternal/pyxb,CantemoInternal/pyxb