Using the CMake support we added some time ago for real with Visual
Studio build revealed there were lot of usability improvements
possible, which have been carried out.

* js/cmake-vs:
  hashmap_for_each_entry(): workaround MSVC's runtime check failure #3
  cmake (Windows): recommend using Visual Studio's built-in CMake support
  cmake (Windows): initialize vcpkg/build dependencies automatically
  cmake (Windows): complain when encountering an unknown compiler
  cmake (Windows): let the `.dll` files be found when running the tests
  cmake: quote the path accurately when editing `test-lib.sh`
  cmake: fall back to using `vcpkg`'s `msgfmt.exe` on Windows
  cmake: ensure that the `vcpkg` packages are found on Windows
  cmake: do find Git for Windows' shell interpreter
  cmake: ignore files generated by CMake as run in Visual Studio