patch 9.1.0258: half-page scrolling broke backward compatibility

Problem:  Support for 'smoothscroll' in (half-)page scrolling
          broke backward compatibility and can be made to work better.
          (after v9.1.215)
Solution: Restore the previous cursor and end-of-buffer behavior for
          half-page scrolling and improve 'smoothscroll' support.
          (Luuk van Baal)

fixes: #14338
closes: #14377

Signed-off-by: Luuk van Baal <luukvbaal@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/change.c b/src/change.c
index daf4fae..dacc06f 100644
--- a/src/change.c
+++ b/src/change.c
@@ -574,8 +574,7 @@
 			    && wp->w_topline < lnume
 			    && win_linetabsize(wp, wp->w_topline,
 					ml_get(wp->w_topline), (colnr_T)MAXCOL)
-				    <= wp->w_skipcol + sms_marker_overlap(wp,
-					win_col_off(wp) - win_col_off2(wp)))))
+				    <= wp->w_skipcol + sms_marker_overlap(wp, -1))))
 		wp->w_skipcol = 0;
 
 	    // Check if a change in the buffer has invalidated the cached