Merging r278763:

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r278763 | rsmith | 2016-08-15 17:13:47 -0700 (Mon, 15 Aug 2016) | 5 lines

PR28978: If we need overload resolution for the move constructor of an
anonymous union member of a class, we need overload resolution for the move
constructor of the class itself too; we can't rely on Sema to do the right
thing for us for anonymous union types.

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llvm-svn: 278817