* backends/vs: Only set platform_toolset if it isn't already set
* interpreter: set backend up after the compiler
Otherwise we won't be able to check which VS toolchain to use.
* docs/using-visual-studio: wrap lines
* docs: recommend the py launcher instead of python3 for windows
* set backend.environment when building a dummy version
* backends/vs: Add support for clang-cl with vs2017 and vs2019 backends
* backends/vs: Add support for ICL (19.x) with vs2015 and vs2017 backends
This allows us to more easily have the documentation in sync with
the source code as people will have to document new features etc
right at the time where they implement it.
Jussi Pakkanen