Used ngettext in a formsets error message

Several languages will distinctly translate '%d or fewer forms'
depending on the variable.
Systematically imported wraps from functools
Fixed #18351 -- Added X-Robots-Tag header to sitemaps

Thanks Michael Lissner for the report and initial patch, and
Tom Mortimer-Jones for working on the patch.
One more changed import location of wraps
Fixed a regression introduced in 9f7a01ef2bed8c0395a970286e8f87fd7d344b3b.
Ensured that the javascript_catalog view doesn't leak translations.
Found a mistake in SQL documentation
Fixed #20305 - Added include for polls/static to MANIFEST.in in tutorial.

Thanks monuszko for the report.