There are three scenarios where ctypes is used in this module:

* get libuuid.uuid_generate_time_safe and uuid_generate_time (if _uuid was not compiled)
* get rpcrt4.UuidCreateSequential (on Windows, depending on how the libuuid lookup failed)
* GetSystemDirectory (on Windows, safe to replace with alternative approach)

I'll happily move the UuidCreateSequential call into _uuid and add it to the Windows build, but it's not clear whether the libuuid lookup is important or not. If anyone knows of scenarios where you can't compile against libuuid but can load it with ctypes, would be great to hear about it!