`DirEntry` metadata `ino` field panicks on Windows

[pchickey]

Inside the Dir::entries iterator, calling dir_entry.metadata()? succeeds, but the .ino() accessor panicks, only on windows, with a message that says:

`ino` depends on a Metadata constructed from an open `File`

[sunfishcode]

Fixed in 1548745 (for DirEntry) and 01a3028 (for Dir).