common, menu: add statusline support

add the possibility to show a statusline when printing a menu

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Jason Hobbs <jason.hobbs@calxeda.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/doc/README.menu b/doc/README.menu
index 0dad6a2..4ddf914 100644
--- a/doc/README.menu
+++ b/doc/README.menu
@@ -69,6 +69,11 @@
  */
 int menu_destroy(struct menu *m);
 
+/*
+ * menu_display_statusline(struct menu *m);
+ * shows a statusline for every menu_display call.
+ */
+void menu_display_statusline(struct menu *m);
 
 Example Code
 ------------