file+noindex, absolute paths and Windows

`file://C:\foo\repo` is not a valid URI.

EDIT:

```haskell
Prelude Network.URI> parseURI "file+noindex:///?/hello/world/"
Just file+noindex:///?/hello/world/

Prelude System.FilePath.Windows> normalise "//?/hello/world/"
"\\\\?\\hello\\world\\"
```

seems to work. Have to be more careful in encoding / decoding paths for `file+noindex` URIs, so maybe then it will work.