[1.6.x] Fixed #22801 -- Added 'www.' to diveintopython.net links

Backport of f97c53c098 from master
[1.6.x] Fixed #22813 -- Updated Pillow URL in documentation

Backport of dfa3505ff1 from master.
[1.6.x] Fixed #22818 -- Clarified you need to cd into the Django clone.

Thanks Josh Parris.

Backport of bcc3d2b978 from master
[1.6.x] Fixed #22349 -- Added a note clarifying `RawQuerySet` has no `__len__`.

Thanks cdestigter for the report.

Backport of 2d425116e2 from master
[1.6.x] Fixed #22842

Backport of 7a1f8414c3b71b6af03e5be9f5f8db115551c410 from master.
[1.6.x] Fixed #14481 -- Documented implicit "through" class created by ManyToManyField.

Thanks to jonathanmorgan for the report and initial patch.

Backport of de90129070 from master
[1.6.x] Fixed #22859 -- Improved crossDomain technique in CSRF example.

Thanks flisky for the report.

Backport of 0be4d64487 from master
[1.6.x] Fixed #22514 -- Prevented indexes on virtual fields [postgres].

Backport of 78c32f1caa from master
[1.6.x] Created import-time test temp dirs in known location

Refs #17215. In the same spirit as 5de31cb8cb.
Backport of 809362518d from master.
[1.6.x] Fixed typo in middleware docs.

Function definition should have an ending colon.

Backport of 48241ec from master
[1.6.x] Improved documentation for QueryDict.

Backport of 7f4e2ef1e9 from master
[1.6.x] Fixed copy/paste typos in StreamingHttpResponse doc.

Backport of e9c730f6be from master
[1.6.x] Fixed #22912 -- Warned about a common mistake in tutorial 5.

Backport of 1e8411259f from master
[1.6.x] Fixed a French translation in contrib.auth

Refs #22929.
[1.6.x] Fixed docs/ref/contrib/auth.txt so that sphinx links work properly.

Backport of 5359188b08 from master
[1.6.x] Removed reference to old middleware

Backport of 0b5bafe993 from master
[1.6.x] Fixed #19489 -- Documented host parameter of assertRedirects().

Thanks mrknacky at gmail.com for the report and gajimenezmaggiora
for the draft patch.

Backport of e3c7af18a3 from master
[1.6.x] Included irc link in paragraph to allow for l10n

Translators may want to change the irc link pointing to a
language-specific channel.
Backport of 232f2028d5 from master.
[1.6.x] Fixed #13755 -- Added a tip for caching responses that vary on AJAX.

Thanks mila for the suggestion.

Backport of db9a1a0c47 from master
[1.6.x] Clarified that LocMemCache is per-process; refs #7639.

Thanks projectgus for the suggestion.

Backport of c37000ab04 from master