patch 9.0.0206: redraw flags are not named specifically

Problem:    Redraw flags are not named specifically.
Solution:   Prefix "UPD_" to the flags, for UPDate_screen().
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index 793a104..ff6aa0d 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -3654,7 +3654,7 @@
 	p_ls = save_p_ls;
 	p_wmh = save_p_wmh;
 	last_status(FALSE);
-	update_screen(VALID);	// redraw the screen NOW
+	update_screen(UPD_VALID);	// redraw the screen NOW
 	redrawcmd();
 	save_p_ls = -1;
     }