patch 9.0.0640: cannot scroll by screen line if a line wraps

Problem:    Cannot scroll by screen line if a line wraps.
Solution:   Add the 'smoothscroll' option.  Only works for CTRL-E and CTRL-Y
            so far.

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    640,
 /**/
     639,
 /**/