Make Application.post_process_urls() compatible with 1.10
Make Application.post_process_urls() compatible with 1.10

Since the RegexURLPattern has no `_callback` attribute anymore the
`get_url_decorator()` wasn't called anymore.

sonofatailor/django-oscar,sasha0/django-oscar,solarissmoke/django-oscar,solarissmoke/django-oscar,sonofatailor/django-oscar,sasha0/django-oscar,solarissmoke/django-oscar,solarissmoke/django-oscar,django-oscar/django-oscar,sonofatailor/django-oscar,sonofatailor/django-oscar,django-oscar/django-oscar,django-oscar/django-oscar,django-oscar/django-oscar,sasha0/django-oscar,sasha0/django-oscar