patch 8.2.4614: redrawing too much when 'cursorline' is set

Problem:    Redrawing too much when 'cursorline' is set and jumping around.
Solution:   Rely on win_update() to redraw the current and previous cursor
            line, do not mark lines as modified. (closes #9996)
diff --git a/src/drawscreen.c b/src/drawscreen.c
index a562c4d..a902397 100644
--- a/src/drawscreen.c
+++ b/src/drawscreen.c
@@ -1468,9 +1468,6 @@
 # define DID_FOLD 3	// updated a folded line
     int		did_update = DID_NONE;
     linenr_T	syntax_last_parsed = 0;		// last parsed text line
-    // remember the current w_last_cursorline, it changes when drawing the new
-    // cursor line
-    linenr_T	last_cursorline = wp->w_last_cursorline;
 #endif
     linenr_T	mod_top = 0;
     linenr_T	mod_bot = 0;
@@ -2245,8 +2242,8 @@
 #endif
 				))))
 #ifdef FEAT_SYN_HL
-		|| (wp->w_p_cul && (lnum == wp->w_cursor.lnum
-						   || lnum == last_cursorline))
+		|| (wp->w_p_cul && lnum == wp->w_cursor.lnum)
+		|| lnum == wp->w_last_cursorline
 #endif
 				)
 	{
@@ -2551,6 +2548,12 @@
 
     // End of loop over all window lines.
 
+#ifdef FEAT_SYN_HL
+    // Now that the window has been redrawn with the old and new cursor line,
+    // update w_last_cursorline.
+    wp->w_last_cursorline = wp->w_p_cul ? wp->w_cursor.lnum : 0;
+#endif
+
 #ifdef FEAT_VTP
     // Rewrite the character at the end of the screen line.
     // See the version that was fixed.