Reviewed/committed
------------------
https://github.com/django/django/pull/9552 - Fixed #28857 -- Fixed invalid SQL when using Cast with complex expressions on PostgreSQL.
https://github.com/django/django/pull/9539 - Refs #28643 -- Added Replace database function.
https://github.com/django/django/pull/9605 - Fixed #29041 -- Changed SelectMultiple widget's multiple attribute to HTML5 boolean syntax.
https://github.com/django/django/pull/8684 - Fixed #28343 -- Add an OS chooser for docs command line examples.
https://github.com/django/django/pull/9602 - Fixed #29038 -- Removed closing slash from HTML void tags.