That's not exactly accurate. In its current form, you couldn't compile OpenBSD's libssl on Windows even if you had a build system for it.
However, I don't think this is a bad thing. To do a massive clean up, you must be able to focus on code that you can actually compile and test. Dead code, code behind ifdefs is likely to rot. If it wasn't very rotten already.
It is better to do a fresh port of a cleaned up code base for modern systems.
