windows: fall back for volume info query

Wine does not currently support FileFsVolumeInformation:

https://github.com/mirrors/wine/blob/0e42fd97c05beb50c0788164647631c00485623b/dlls/ntdll/file.c#L2679

so check io_status and fall back to previous behavior if not implemented
Merge pull request #22 from JuliaLang/volinfo_nimp

Work-around for unsupported volume info query