patch 9.0.1568: with 'smoothscroll' cursor may move below botline

Problem:    With 'smoothscroll' cursor may move below botline.
Solution:   Call redraw_later() if needed,  Compute cursor row with adjusted
            condition. (Luuk van Baal, closes #12415)

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1568,
 /**/
     1567,
 /**/