Fixed #22322 -- Fixed incorrect explanation of what managed=False does.

refs #14305.

Thanks Adrian Klaver for the report.
Fixed #12030 -- Validate integer field range at the model level.

Thanks to @timgraham for the review.
Add some syncdb deprecation stuff into the deprecation doc
Fixed #22331 -- Made MigrationAutodetector ignore unmanaged models.

This commit reverts 69d4b1c and tackle the issue from a different angle.
Models remain present in the project state, but are now ignored by the
autodetector.
Fixed field deconstruction tests failures introduced by 1506c71a95.

refs #12030.
Fixed #22335 -- Fixed popen_wrapper error on non-English Windows systems.
Merge pull request #2481 from zsiciarz/ticket-22335

Fixed #22335 -- Fixed popen_wrapper error on non-English Windows systems.
Fixed Python 3.4 test failure.
Fixed #22029 -- Removed obsolete advice on registering migrate/syncdb signal handlers.

All signals should now be registered in AppConfig.ready().

Thanks un33k for the report.
Fixed the PostGIS circular imports caused by 1506c71a95.

Thanks to @loic for the help and @timgraham for the review.

refs #12030.
Fixed #22114 -- Stopped adding trailing slashes in URLField.to_python

Thanks coredumperror at gmail.com for the report and Tim Graham
for the review.
Forgotten slash removal in d320863878
Fixed #21239 -- Maintained atomicity when closing the connection.
Fixed #22321 -- Wrapped exceptions in _set_autocommit.

Refs #21202.
Fixed #21202 -- Maintained atomicity when the server disconnects.

Thanks intgr for the report.

This commit doesn't include a test because I don't know how to emulate a
database disconnection in a cross-database compatible way.