patch 9.0.1309: scrolling two lines with even line count and 'scrolloff' set

Problem:    Scrolling two lines with even line count and 'scrolloff' set.
Solution:   Adjust how the topline is computed. (closes #10545)
diff --git a/src/version.c b/src/version.c
index be98fc8..3303bef 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1309,
+/**/
     1308,
 /**/
     1307,