patch 9.1.1162: completion popup not cleared in cmdline

Problem:  When an info popup spans into the cmdline area and ESC is
          pressed, some content remains visible on screen (yu3s)
Solution: Add popup_overlays_cmdline() check in screen_fill() to prevent
          prematurely clearing the clear_cmdline flag (glepnir).

fixes: #15627
closes: #16765

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index 11679c6..14432fc 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -74,4 +74,6 @@
 int popup_win_closed(win_T *win);
 void popup_set_title(win_T *wp);
 void popup_update_preview_title(void);
+int popup_overlaps_cmdline(void);
+
 /* vim: set ft=c : */