[1.7.x] Ignored STATIC_ROOT and MEDIA_ROOT in makemessages

Also alleviate issues with weird file names typically found in
MEDIA_ROOT directories (#23010).
Thanks Tim Graham for the review.
Backport of 28efafa24c from master.
[1.7.x] Fixed #22998 -- Updated the fast_delete logic for GFKs

Backport of 6e2b82fdf6 from master
[1.7.x] PEP8 cleanup

Backport of f8df55050c from master
[1.7.x] Added forgotten files from commit 28efafa24c83

Backport of c5d8e4a0d1 from master.
[1.7.x] Added Chrome/IE support for a selenium test.

Backport of 5954aa6db0 from master
[1.7.x] Fixed #23023 -- Added warning against local-memory cache.

Thanks django at kerz.id.au.

Backport of 7d0519c725 from master
[1.7.x] Fixed #23041: Bad base dependencies for proxy models
[1.7.x] Fixed reference to pk in RedirectView.get_redirect_url doc.

Backport of d9f78d5344 from master
[1.7.x] Added 1.6.6 release notes for #22998 (also forwardported those for #13794).

Backport of c62c480b2b from master
[1.7.x] Alphabetized django.utils sections.

Backport of e7827b9494 from master
[1.7.x] Edited setup.py in reuseable apps tutorial to use a context manager for open().

Backport of b8d255071e from master