Merging r370355:

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r370355 | joerg | 2019-08-29 15:22:30 +0200 (Thu, 29 Aug 2019) | 5 lines

Allow replaceAndRecursivelySimplify to list unsimplified visitees.

This is part of D65280 and split it to avoid ABI changes on the 9.0
release branch.

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llvm-svn: 370447