* It normally should not be necessary to use the _Z form of the BOOST_PP_ENUM macro, although it is perfectly legal and helpful to do so, but in this case it is necessary as a workaround for a bug in the new VC++ standard conforming preprocessor. The bug manifests itself when testing the TTI library, which internally uses the Boost MPL code. The bug in the new VC++ standard conforming compiler is fixed in the VS2019 preview product, so that fix is sure to find its way to the official VS2019 product sometime soon. In the meantime this "fix" shortens the macro expansion somewhat and, while it should not be necessary, is still helpful.
* Fix for appveyor.yml file
* Added VS2019 tests, also with new preprocessor. Further MPL Fixes for new preprocessor bug, which are also useful and will speed up preprocessing.
* Can't seem to test msvc-10.0 or msvc-11.0 any more with Appveyor
* Update description
Edward Diener
akumta
Peter Dimov
Eric Niebler
Jeremiah Willcock