Store appointments for the current day in a vector

This allows for more efficient access to items at specific positions.

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

src/utils.c

@@ -102,7 +102,7 @@ void free_user_data(void)
 {
 	unsigned i;
 
-	day_free_list();
+	day_free_vector();
 	event_llist_free();
 	apoint_llist_free();
 	recur_apoint_llist_free();