Remove Differ and Changer interfaces

Add the methods to the Driver interface
to force the drivers to implement the methods

devmapper/driver.go

@@ -2,6 +2,7 @@ package devmapper
 
 import (
 	"fmt"
+	"github.com/dotcloud/docker/archive"
 	"github.com/dotcloud/docker/graphdriver"
 	"os"
 	"path"
@@ -60,6 +61,14 @@ func (d *Driver) DiffSize(id string) (int64, error) {
 	return -1, fmt.Errorf("Not implemented")
 }
 
+func (d *Driver) Diff(id string) (archive.Archive, error) {
+	return nil, fmt.Errorf("Not implemented)")
+}
+
+func (d *Driver) Changes(id string) ([]archive.Change, error) {
+	return nil, fmt.Errorf("asdlfj)")
+}
+
 func (d *Driver) mount(id, mp string) error {
 	// Create the target directories if they don't exist
 	if err := os.MkdirAll(mp, 0755); err != nil && !os.IsExist(err) {