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/ucov/main.c

@@ -192,6 +192,7 @@ int main(
     Device_Set_Object_Instance_Number(BACNET_MAX_INSTANCE);
     Init_Service_Handlers();
     dlenv_init();
+    atexit(datalink_cleanup);
     Send_UCOV_Notify(&Handler_Transmit_Buffer[0], &cov_data);
 
     return 0;