Fixed #11915: generic Accept-Language matches country-specific variants
Merge pull request #1152 from ambv/issue11915

Fixed #11915: generic Accept-Language matches country-specific variants
Fix #20447: URL names given to contrib.auth.views are now resolved.

This commit also adds tests for the redirect feature of most auth views.
It also cleans up the tests, most notably using @override_settings instead
of ad-hoc setUp/tearDown methods.

Thanks to caumons for the report.