channeldb: add int64 to codec

channeldb/codec.go

@@ -108,7 +108,7 @@ func WriteElement(w io.Writer, element interface{}) error {
 			return err
 		}
 
-	case uint64:
+	case int64, uint64:
 		if err := binary.Write(w, byteOrder, e); err != nil {
 			return err
 		}
@@ -280,7 +280,7 @@ func ReadElement(r io.Reader, element interface{}) error {
 			return err
 		}
 
-	case *uint64:
+	case *int64, *uint64:
 		if err := binary.Read(r, byteOrder, e); err != nil {
 			return err
 		}