patch 8.1.0256: using setline() in TextChangedI splits undo

Problem:    Using setline() in TextChangedI splits undo.
Solution:   Use another solution for undo not working properly.
diff --git a/src/version.c b/src/version.c
index 76d47dd..8e21e98 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    256,
+/**/
     255,
 /**/
     254,