Add support for caption rows in list boxes

This adds support for rows that cannot be selected. Such rows can be
used for section headings and the like.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/ui-todo.c

@@ -177,6 +177,11 @@ void ui_todo_draw(int n, WINDOW *win, int y, int hilt, void *cb_data)
 	*((llist_item_t **)cb_data) = i->next;
 }
 
+enum listbox_row_type ui_todo_row_type(int i, void *cb_data)
+{
+	return LISTBOX_ROW_TEXT;
+}
+
 int ui_todo_height(int n, void *cb_data)
 {
 	return 1;