Add new experimental flag ext_partition_types_ab

Change-Id: Ib85b2a778e1306444ac0cbbfb212e739a0f0009c
diff --git a/configure b/configure
index 8b65a32..6a5c1a7 100755
--- a/configure
+++ b/configure
@@ -278,6 +278,7 @@
     loop_restoration
     ext_partition
     ext_partition_types
+    ext_partition_types_ab
     unpoison_partition_ctx
     ext_tile
     motion_var