Adding a way to decode to a specified version.

This is largely needed as a way to get a versioned client without
requiring everyone to switch to versioned types at once.

pkg/api/meta/restmapper_test.go

@@ -33,6 +33,10 @@ func (fakeCodec) Decode([]byte) (runtime.Object, error) {
 	return nil, nil
 }
 
+func (fakeCodec) DecodeToVersion([]byte, string) (runtime.Object, error) {
+	return nil, nil
+}
+
 func (fakeCodec) DecodeInto([]byte, runtime.Object) error {
 	return nil
 }