net: Interface.Flags always 0 on Windows 8

Go version: 1.4

The following code works on Windows 7:

``` go
package main
import "fmt"
import "net"
func main() {
    ifs, _ := net.Interfaces()
    for _, i := range ifs {
        fmt.Println(i.Flags)
    }
}
```

Tried both "run as administrator" and "compatibility mode" to see whether this was a side effect but never saw any flags when running on Windows 8.
