The liferay-ui:custom-attribute* tags are not really friendly for extension. They always go all-or-nothing: If you create extensions using custom attributes, you cannot use the tags "for all other fields, that you don't handle manually".
The change is to add an attribute "ignore" to the tags - all attributes named as "ignore" will not be displayed, e.g. for users_admin/user/custom_fields.jsp, this is what it looks like:
It will output all custom attributes apart from the ignored ones. Those can be handled separately, e.g. on a separate custom page while the others can still stay on the "custom fields" page.
(identical change proposed for liferay-ui:custom-attributes-available)