master fails to build with libevent 1: event_free not a known function
```
compat_libevent.c: In function ‘run_runnable_cb’:
compat_libevent.c:576:3: error: implicit declaration of function ‘event_free’ [-Werror=implicit-function-declaration]
compat_libevent.c:576:3: error: nested extern declaration of ‘event_free’ [-Werror=nested-externs]
```
Looks like the bug crept in during 7920ea55.
And this patch makes it compile:
```
--- a/src/common/compat_libevent.c
+++ b/src/common/compat_libevent.c
@@ -573,7 +573,7 @@ run_runnable_cb(evutil_socket_t s, short what, void *arg)
void *cb_arg = r->arg;
(void)what;
(void)s;
- event_free(r->ev);
+ tor_event_free(r->ev);
tor_free(r);
cb(cb_arg);
```
issue