Accesscontrol

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- Fix a bug in ZopeSecurityPolicy.py. Global variable `rolesForPermissionOn`
could be overridden if `__role__` had custom rolesForPermissionOn.

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- Add Anonymous as a default role for Public permission.

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- Exclude compiled `.so` and `.dll` files from source distributions.

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- Added `manifest.in` to ensure the inclusion of the `include` directory into
the release.

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- Apply changes made available in `Products.Zope_Hotfix_20111024` and make them
more robust.

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- Return the created user in _doAddUser.

- Added IUser interface.

- LP 659968: Added support for level argument to the ``__import__`` function
as introduced in Python 2.5. Currently only level=-1 is supported.