builtins/url: Change parameter name so it does not conflict with an url ...

...parameter called "name".

This reflects the same name used in https://github.com/coffin/coffin/blob/master/coffin/template/defaultfilters.py, but it's probably as bad as a solution, because now you cannot use url() with a "view_name" url parameter. Maybe a better way to implement it would be to pop the first *args element (that'd raise if no arg is provided) and use it as the view name.