Fixed #20439 -- Started deprecation of IPAddressField
Fixed #21187 -- Import CursorWrapper from django.db.backend.utils

The import was done from util instead of utils leading to
PendingDeprecationWarning.
Fixed #21162 -- Better emulation of staticfiles middleware.

Code had been added in e909ceae9b. Solves test suite failures observed
on Windows.

Thanks Michael Manfre for the report. Refs #20739.
Note about static files dirs paths on Windows.

Added it to the settings reference. We used to have it in comment form
in our old, bigger default project template settings.py file.
Fixed #20931 -- Fixed select widgets nested choice rendering

ChoiceFieldRenderer was not rendering nested choices. Added recursion
to ChoiceFieldRenderer to take nested choices and render them as
<ul>'s.