Added explicit datalink_cleanup to all demo applications.

Moved bip_cleanup() to port specific files.
This works better for bacnet-stack DLLs.

bacnet-stack/demo/timesync/main.c

@@ -148,6 +148,7 @@ int main(
     Device_Set_Object_Instance_Number(BACNET_MAX_INSTANCE);
     Init_Service_Handlers();
     dlenv_init();
+    atexit(datalink_cleanup);
     /* configure the timeout values */
     last_seconds = time(NULL);
     timeout_seconds = apdu_timeout() / 1000;