Fix missing line in runtime header in compiler series

code/compiler/08/runtime.h

@@ -55,6 +55,7 @@ struct stack {
     struct node_base** data;
 };
 
+void stack_init(struct stack* s);
 void stack_free(struct stack* s);
 void stack_push(struct stack* s, struct node_base* n);
 struct node_base* stack_pop(struct stack* s);