Allow for filtering TODO items

The item filters now apply to both appointments and TODO items. Also,
add a new type mask "todo" and the following new filter options:

* --filter-priority
* --filter-completed
* --filter-uncompleted

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

src/calcurse.c

@@ -332,7 +332,7 @@ static inline void key_generic_reload(void)
 	recur_event_llist_init();
 	todo_init_list();
 
-	io_load_todo();
+	io_load_todo(NULL);
 	io_load_app(NULL);
 	io_unset_modified();
 	ui_todo_load_items();
@@ -683,7 +683,7 @@ int main(int argc, char **argv)
 	config_load();
 	wins_erase_status_bar();
 	io_load_keys(conf.pager);
-	io_load_todo();
+	io_load_todo(NULL);
 	io_load_app(NULL);
 	io_unset_modified();
 	wins_slctd_set(conf.default_panel);