Fixed #22971 -- Properly parsed RFC 2388 encoded headers

Thanks homm for the report, Cea Stapleton for patch improvements
and Ian Cordasco, Christian Schmitt and Tim Graham for the review.
Fixed #23265 -- Used system-specific encoding in runserver

Thanks SpaceFox for the report.
Fixed #21132 -- Removed the useless app_name argument to AdminSite.

Thanks MarkusH for the report and Florian for review.
Fixed #21579 -- Made LocaleMiddleware respect script prefix.

Thanks buettgenbach at datacollect.com for the report and patch.
Fixed #23260: Added generator support to defaultfilters.unordered_list.
Fixed #23291 -- Don't add Unicode varname/value to environment.

Windows doesn't like that and it causes 114 failures in the
admin_scripts tests with Python 2.x.
Fixed a grammar error in docs/ref/forms/api.txt.
Fixed #23270 -- Added selected reverse relations to the only fields