patch 8.1.1646: build failure

Problem:    build failure
Solution:   Add changes to structure.
diff --git a/src/version.c b/src/version.c
index 6165133..52bce3b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1646,
+/**/
     1645,
 /**/
     1644,