0004567: Replace boost::filesystem with std::experimental::filesystem in MSVC 2017
Description
Since VS2015 we have the experimental namespace which is almost the same as the boost::filesystem one. A few methods are called differently, but overall it should be possible to use a namespace alias for almost all occurrences.
Done, Linux and macOS still use boost::filesystem. As of GCC 5.3 it should be possible to use the std::experimental header, but this requires a bit of autoconf trickery and preprocessor definitions.
