patch 8.2.3614: zindex of popup windows not used when redrawing popup menu

Problem:    zindex of popup windows not used when redrawing popup menu.
Solution:   Check the zindex when redrawing the popup menu.  (closes #9129,
            closes #9089)
diff --git a/src/popupmenu.c b/src/popupmenu.c
index bb1a611..86a9cbb 100644
--- a/src/popupmenu.c
+++ b/src/popupmenu.c
@@ -382,9 +382,9 @@
  * "row"/"col" is under the popup menu.
  */
     int
-pum_under_menu(int row, int col)
+pum_under_menu(int row, int col, int only_redrawing)
 {
-    return pum_will_redraw
+    return (!only_redrawing || pum_will_redraw)
 	    && row >= pum_row
 	    && row < pum_row + pum_height
 	    && col >= pum_col - 1