message: Adding comments to what is included from unistd.h
diff: // We should include unistd.h, but it doesn't really work well for cross compilation, as
  // requires us to carry around unistd.h, which is not available on Windows out of the box.
  #include <unistd.h>
  +
  +// Just for the reference: these lines are eventually included from unistd.h
  // #define _SC_NPROCESSORS_ONLN 58
  // long sysconf(int);
  #endif // !_MSC_VER
  