Expand cpuworker API to allow other work types

src/or/cpuworker.h

@@ -14,6 +14,12 @@
 
 void cpu_init(void);
 void cpuworkers_rotate_keyinfo(void);
+struct workqueue_entry_s;
+enum workqueue_reply_t;
+struct workqueue_entry_s *cpuworker_queue_work(
+                    enum workqueue_reply_t (*fn)(void *, void *),
+                    void (*reply_fn)(void *),
+                    void *arg);
 
 struct create_cell_t;
 int assign_onionskin_to_cpuworker(or_circuit_t *circ,