Added condition to prevent checking the existence of a file name of a
file like object when the name attribute is None. This is necessary
because a SpooledTemporaryFile won't exist on the file system or have a
name until it has reached its max_size. Also added tests.

Small doc changes missed in 66076268.

Refs #17906.

If memory serves, the corresponding warning disappeared in Django 1.7.

Previously, when createcachetable and flush operated on non-default
databases, they weren't atomic.

refs #17365, #17366, #18727.

Switched {% cycle %} and {% firstof %} tags to auto-escape their variables per deprecation timeline.

refs #17906.

refs #20288.

refs #21386.

refs #4592.

refs #19689.

refs #19934.

refs #5789.

refs #15201.

Also removed related utility functions:
* django.utils.html.fix_ampersands
* django.utils.html.clean_html

Also removed the backward compatible shims introduced to rename the
attributes ChangeList.root_query_set and ChangeList.query_set.

Thanks to bak1an for the patch.

Fixed #21840 -- Moved dunder methods from SimpleLazyObject to LazyObject...

Thanks bmispelon for the suggestion.