updated for version 7.4.640

Problem:    After deleting characters in Insert mode such that lines are
            joined undo does not work properly. (issue 324)
Solution:   Use Insstart instead of Insstart_orig. (Christian Brabandt)

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    640,
 /**/
     639,
 /**/