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/ptransfer/main.c

@@ -222,6 +222,7 @@ int main(
     address_init();
     Init_Service_Handlers();
     dlenv_init();
+    atexit(datalink_cleanup);
     /* configure the timeout values */
     last_seconds = time(NULL);
     timeout_seconds = (apdu_timeout() / 1000) * apdu_retries();
@@ -380,7 +381,6 @@ int main(
             last_seconds = current_seconds;
         }
     }
-
     if (Error_Detected)
         return 1;
     return 0;