Replace `class_eval` with `define_method` for enum

Also improve the example to show as shell command [ci skip]

https://github.com/rails/rails/commit/db41eb8a6ea88b854bf5cd11070ea4245e1639c5#commitcomment-4502683

We used to support the `BACKTRACE` environment variable but when
we switched to MiniTest it got removed: f9382cd7

This commit adds back the functionality to show the unfiltered backtrace when needed.
This also works when you run your tests with `rake`:

* `BACKTRACE=1 bin/rake test`
* `BACKTRACE=1 ruby -Itest ...`

Not adding webconsole by default in new apps

Revert "ActiveRecord::Base#<=> has been removed.  Primary keys may not be in order," -- will be replaced with a check to ensure that the keys used for comparison are integers, and only fail if they are not.

This reverts commit 6256734e.

Conflicts:
	activerecord/CHANGELOG.md

Explicit mapping for enum

Extend ActiveRecord::Base#cache_key to take an optional list of timestamp attributes of which the highest will be used.

Added Numeric#in_milliseconds, like 1.hour.in_milliseconds, so we can feed them to JavaScript functions like getTime().

This reverts commit c2b5a8e6, reversing
changes made to 1918b12c.

See: https://github.com/rails/rails/pull/9660#issuecomment-27627493

Added ActiveRecord::Base#enum for declaring enum attributes where the values map to integers in the database, but can be queried by name

Minor doc fix of ActiveModel::Naming. [ci skip]

Conflicts:
	activemodel/lib/active_model/naming.rb

Change ActionController::Parameters#require behavior when value is empty

was using nullify strategy

This caused a regression in applications trying to upgrade.

Also if the user set the dependent option as destroy he expects to get
the records removed from the database.

Remove warnings on ruby trunk

Fix railties build

Fix typo in method description in Responder class

More Warnings removed for ruby trunk

Fixes a typo in the description for the call class method in Responder.