Move FileInfoTruncated to files package

This is where it's used, and it clarifies that it's never used over the
wire.

cmd/stindex/main.go

@@ -44,7 +44,7 @@ func main() {
 	if *device == "" {
 		log.Printf("*** Global index for folder %q", *folder)
 		fs.WithGlobalTruncated(func(fi files.FileIntf) bool {
-			f := fi.(protocol.FileInfoTruncated)
+			f := fi.(files.FileInfoTruncated)
 			fmt.Println(f)
 			fmt.Println("\t", fs.Availability(f.Name))
 			return true
@@ -56,7 +56,7 @@ func main() {
 		}
 		log.Printf("*** Have index for folder %q device %q", *folder, n)
 		fs.WithHaveTruncated(n, func(fi files.FileIntf) bool {
-			f := fi.(protocol.FileInfoTruncated)
+			f := fi.(files.FileInfoTruncated)
 			fmt.Println(f)
 			return true
 		})