Rename files which violate MAX_PATH on Windows

When downloading a zip of the repo it's likely these paths will violate
MAX_PATH on windows as discussed
[here](http://www.codinghorror.com/blog/2006/11/filesystem-paths-how-long-is-too-long.html).
This specifically fixes a problem seen when running the [perf automation
scripts](https://github.com/brodyberg/fsharp/tree/SetAndMapPerformanceTests/tests/perf/MapSet/Automate)
on Windows.