Add missing AllocateIDs API.

impl/prod/raw_datastore.go

Index: impl/prod/raw_datastore.go
diff --git a/impl/prod/raw_datastore.go b/impl/prod/raw_datastore.go
index ce4f1df6fd90b0ec0d16feeeddeeea8ae646c1cc..3a9b1d96c355155c41ff02eb83bcf4bbb663edc1 100644
--- a/impl/prod/raw_datastore.go
+++ b/impl/prod/raw_datastore.go
@@ -46,6 +46,16 @@ func idxCallbacker(err error, amt int, cb func(idx int, err error)) error {
 	return err
 }
 
+func (d rdsImpl) AllocateIDs(incomplete *ds.Key, n int) (start int64, err error) {
+	par, err := dsF2R(d, incomplete.Parent())
+	if err != nil {
+		return
+	}
+
+	start, _, err = datastore.AllocateIDs(d, incomplete.Last().Kind, par, n)
+	return
+}
+
 func (d rdsImpl) DeleteMulti(ks []*ds.Key, cb ds.DeleteMultiCB) error {
 	keys, err := dsMF2R(d, ks)
 	if err == nil {