------------------
- Make ``PyProxyBase.__iter__()`` return the result of
``PyProxyBase._wrapped.__iter__`` if available, otherwise falling back to
Python internals. The previous implementation always created a generator.
- In ``PyProxyBase.__setattr__()``, allow setting of properties on the
proxy itself. This is needed to properly allow proxy extensions as was
evidenced int he ``zope.security.decorator`` module.