Revert the changes from commit a2a90f41 (Tests: require C++14 for the
Tutorial, 2019-03-21, v3.15.0-rc1~41^2~2) for the content in its new
home.  In commit d50b31be (Clang: For MSVC ABI do not use modes older
than C++14, 2019-07-23) we fixed the C++ standard selection for GNU-like
Clang with the MSVC ABI so the test code itself no longer needs to do
it.  In particular, changing the tests in this way broke the tutorial's
narrative.