DLL names are different on Windows (Rust only?)

[BatmanAoD]

Windows shared libs are of the form <name>.dll, not lib<name>.so. This can be handled in the platform checking logic near the top of __init__.py (which I think should, in addition to setting ext, create some kind of lib-prefix variable to indicate whether lib should be prepended to the name).

This doesn't seem to affect %cffi, but I'm not sure why.