This backports parts of zope 4 commits bb7837c66 (Explicitly make all classes new-style., 2017-09-15) and 173658008 (Fix unpickling of instances those base class changed to a new-style class. (#208), 2017-10-24) for zope2.

This is done for two reasons:

• so that business template XML are same when exported from zope4 and from zope2
• so that a business template created from zope4 can still be installed on zope2.