In 3.4.3, the only file I replaced was user/externallib.php
I guess I should note that I didn't test all the new fields, just `phone1` and I think `institution`. But like I said, before this change some fields like `city`, which were supposedly already supported, were not working at all for me. Putting in your modified user/externallib.php made `city` work too. It also eliminated some unspecified errors using space characters in custom field values.