mconf/nconf: mark empty menus/menuconfigs different from non-empty ones

Submenus are sometimes empty and it would be nice if there is
something that notifies us that we should not expect any content
_before_ we enter a submenu.

A new function menu_is_empty() was introduced and empty menus and
menuconfigs are now marked by "----" as opposed to non-empty ones that
are marked by "--->".

This scheme was suggested by "Yann E. MORIN" <yann.morin.1998@free.fr>.

Signed-off-by: Dirk Gouders <dirk@gouders.net>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index b5c7d90..6d11c8f 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -430,6 +430,22 @@
 	return true;
 }
 
+/*
+ * Determine if a menu is empty.
+ * A menu is considered empty if it contains no or only
+ * invisible entries.
+ */
+bool menu_is_empty(struct menu *menu)
+{
+	struct menu *child;
+
+	for (child = menu->list; child; child = child->next) {
+		if (menu_is_visible(child))
+			return(false);
+	}
+	return(true);
+}
+
 bool menu_is_visible(struct menu *menu)
 {
 	struct menu *child;