[1.5.x] Fixed bug causing CSRF token not to rotate on login.

Thanks Gavin McQuillan for the report.

Backport of ac4fec5ca2 from master
[1.5.x] Added a warning regarding session security and subdomains.

Backport of a3372f67cb from master
[1.5.x] Fixed #21212 -- Documented the reverse name for OneToOneField.

Thanks bjb at credil.org for the report.

Backport of f8632572ad from master
[1.5.x] Fixed #21296 -- Added docs for PostgreSQL and unix domains sockets.

Backport of 1e39982b6e from master
[1.5.x] Fixed #21253 -- PBKDF2 with cached HMAC key

This gives a 2x speed increase compared to the existing implementation.

Thanks to Steve Thomas for the initial patch and Tim Graham for finishing it.

Backport of 1e4f53a6eb8d1816e51eb8bd8f95e704f6b89ead from master.
Oracle defer test failure; refs #16436.

Oracle doesn't like grouping by TextField, so use CharFields instead in
models.

Backport of 728d3fe1bac6b5f23dbd088e11860cfba51cf7b5 from master
[1.5.x] Fixed #21304 -- Typo in docs/topics/testing/advanced.txt

Thanks joao at silvaneves.org for the report.

Backport of 9704c49d59 from master
[1.5.x] Added 1.5.5 and 1.4.9 release notes

Backport of 2eb8f15516 from master
Fixed #13245: Explained Oracle's behavior w.r.t db_table
and how to prevent table-name truncation

Thanks russellm & timo for discussion, and timo for review.

Backported from master 317040a73b77be8f8210801793b2ce6d1a69301e
[1.5.x] Bumped release date for 1.5.5 & 1.4.9.

Backport of 4ce5c119b5 from master
[1.5.x] Bump everything for 1.5.5 bugfix release.
[1.5.x] Bump version post-release.
[1.5.x] Fixed typo in docs/releases/1.4.9.txt.

Backport of 3b0293370a from master
[1.5.x] Fixed #21325 -- Added missing argument to permission_required decorator.

Backport of cc2049cdd7 from master
[1.5.x] Fixed #21335 -- Use importlib from python3 when using python3

Backport of 3351e94ffa from master.
Revert "[1.5.x] Fixed #21335 -- Use importlib from python3 when using python3"

This reverts commit 1ef737416ab56a6becee36876769909a37541465.
This would require changing some import_module calls (relative
syntax, see ec0a3f50852), too much for a stable release.
[1.5.x] Fixed #21337 -- Documented removal of django.core.servers.basehttp.WSGIServerException

refs 2ca00faa913754cd5860f6e1f23c8da2529c691a

Backport of b47a052eb5 from master
[1.5.x] Fixed #21316 -- Documented that modifying safe strings makes them unsafe.

Thanks dev@simon.net.nz for the suggestion and vijay_shanker for the patch.

Backport of 1edef50880 from master
[1.5.x] Documented the limitation on sep argument to Signer

Co-Authored-By: Gavin Wahl <gwahl@fusionbox.com>

Backport of e9a356a695 from master
[1.5.x] Fixed #21294 -- Clarified the logout next_page argument.

Thanks wim at go2people.nl for the report.

Backport of 51e6575472 from master