[ci skip]

Fix duplicable? for Complex and Rational

quiet generators log in test

Remove warning in ActiveJob

This quiet the following log.

```
   create  app/mailers/notifier_mailer.rb
   invoke  erb
   create    app/views/notifier_mailer
identical    app/views/layouts/mailer.text.erb
identical    app/views/layouts/mailer.html.erb
   create    app/views/notifier_mailer/foo.text.erb
   create    app/views/notifier_mailer/foo.html.erb
   invoke  test_unit
   create    test/mailers/notifier_mailer_test.rb
   create    test/mailers/previews/notifier_mailer_preview.rb
```

Currently it causes:

```
activejob/Rakefile:5: warning: already initialized constant ACTIVEJOB_ADAPTERS
```

Document and update API for `skip_parameter_encoding`

This commit changes `parameter_encoding` to `skip_parameter_encoding`.
`skip_parameter_encoding` will set encoding on all parameters to
ASCII-8BIT for a given action on a particular controller.  This allows
the controller to handle data when the encoding of that data is unknown,
for example file systems or truly binary parameters.

See [this test](https://gist.github.com/utilum/78918f1b64f8b61ee732cb266db7c43a).

fix fixtures loading for models with same table names in different databases

Updated the docmentation because "options supports" is not grammatically
correct.

Add all the available options, and correct the samples of the
`javascript_include_tag`.

Ruby 2.4 compatibility

Very similar to PR #25758, see more in depth reasoning there.