Improvement: update for API change - remove `PEP_SESSION.sync_obj` (closes #14)

src/Adapter.cc

@@ -135,7 +135,7 @@ namespace pEp {
         int _cb_pass_sync_event_to_engine(::SYNC_EVENT ev, void *management)
         {
             if (ev != nullptr) {
-                ::do_sync_protocol_step(session(), nullptr, ev);
+                ::do_sync_protocol_step(session(), ev);
             }
             return 0;
         }

src/Adapter.hxx

@@ -44,7 +44,7 @@ namespace pEp {
             // 3. Enter Sync Event Processing Loop (do_sync_protocol())
             // this internally calls _retrieve_next_sync_event
             pEpLog("sync protocol loop started");
-            ::do_sync_protocol(session(), (void *)obj);
+            ::do_sync_protocol(session());
             pEpLog("sync protocol loop ended");
 
             // 4. unregister_sync_callbacks()