Merging r155728:

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r155728 | rsmith | 2012-04-27 12:33:05 -0700 (Fri, 27 Apr 2012) | 4 lines

PR12224 (sort of): Diagnose inheriting constructor declarations in C++11 mode.
We do not support IRGen for these, and get some parts of the semantic analysis
wrong.

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llvm-svn: 155731