fix resource leak in os.(*File).Close

Signed-off-by: Achille Roussel <achille.roussel@gmail.com>

src/os/file_windows.go

@@ -39,6 +39,10 @@ type file struct {
 	name   string
 }
 
+func (f *file) close() error {
+	return f.handle.Close()
+}
+
 func NewFile(fd uintptr, name string) *File {
 	return &File{&file{unixFileHandle(fd), name}}
 }