Add **kw support to DeclarativeMeta.__init__
Added a ``**kw`` argument to the :meth:`.DeclarativeMeta.__init__` method.
This allows a class to support the :pep:`487` metaclass hook
``__init_subclass__``. Pull request courtesy Ewen Gillies.
Fixes: #5357
Closes: #5363
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5363
Pull-request-sha:
0ad05a768316cba03a4d312ab39d3e8fbca7ac54
Change-Id: I1654befe9eb1c8b8e7fc0784bdbe64284614f0ea
(cherry picked from commit
67504137e96547664754691bdd3269b473a488d1)