[Issue 1441] [module] Allow 'private' to restrict class visibility outside module or outer class

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=1441
Issue 1441 depends on issue 2830, which changed state.

Issue 2830 Summary: private attribute doesn't work for structs/unions/classes
https://issues.dlang.org/show_bug.cgi?id=2830

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

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