patch 9.0.0671: negative topline using CTRL-Y with 'smoothscroll' and 'diff'

Problem:    Negative topline using CTRL-Y with 'smoothscroll' and 'diff'.
            (Ernie Rael)
Solution:   Only use 'smoothscroll' when 'wrap' is set.
diff --git a/src/version.c b/src/version.c
index a52b707..5ddf40b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    671,
+/**/
     670,
 /**/
     669,