Call event_set_mem_functions during initialization

changes/ticket8415

@@ -0,0 +1,4 @@
+  o Minor features (memory management):
+    - Get libevent code to use the same memory allocator that
+      Tor code is using by calling event_set_mem_functions()
+      during initialization. Resolves ticket 8415.

src/core/mainloop/main.c

@@ -4242,6 +4242,11 @@ tor_run_main(const tor_main_configuration_t *tor_cfg)
                strerror(-bt_err));
     }
   }
+
+#ifdef EVENT_SET_MEM_FUNCTIONS_IMPLEMENTED
+  event_set_mem_functions(tor_malloc_, tor_realloc_, tor_free_);
+#endif
+
   init_protocol_warning_severity_level();
 
   update_approx_time(time(NULL));