Improve error message for #or when it is structurally incompatible

When you are using scopes and you chaining these scopes it is hard to
know which are the values that are incompatible. This way you can read
the message and know for which values you need to look for.

[Herminio Torres]

This reverts commit 5d41cb3b.

This implementation does not properly handle cases involving predicates
which are not associated with a bind param. I have the fix in mind, but
don't have time to implement just yet. It will be more similar to #22823
than not.

Empty strings / data structures should be treated differently than nils.
We don't really need these calls here (don't pass in blank strings).

Instead of checking whether the class has recycle! or not, we can just
always add the method to all controller classes when the test harness is
loaded.  Technically this means that the controller test harness will
not work with controllers that do not inherit from AC::Metal, but then,
I'm not sure that is supported anyway.

Mixing in the module one will ensure that we don't break method caches,
and eliminates a runtime check so it should speed up tests (slightly).

Add HTTP status name to output of tests

Prevent static middleware from attempting to serve a request with a null byte

While the predicates are an arel equality node where the left side is a
full arel attribute, the binds just have the name of the column and
nothing else. This means that while splitting the predicates can include
the table as a factor, the binds cannot. It's entirely possible that we
might be able to have the bind params carry a bit more information (I
don't believe the name is used for anything but logging), and that is
probably a worthwhile change to make in the future.

However the simplest (and likely slightly faster) solution is to simply
use the indices of the conflicts in both cases. This means that we only
have to compute the collision space once, instead of twice even though
we're doing an additional array iteration. Regardless, this method isn't
a performance hotspot.

Close #22823.

[Ben Woosley & Sean Griffin]

Also, refactor logic to convert between symbol and response code,
via the AssertionResponse class

AC::Parameters#at_json: restore Rails 4.2’s value

File paths cannot contain null byte characters and methods that do path
operations such as Rack::Utils#clean_path_info will raise unwanted
errors.

Fixes #23026

See discussion at #23026

Closes #23027.

This does not restore complete backwards compatibility. It simply passes
the contets of the `TEST` env to the new runner.

Closes #23021.

Make default scopes + STI happy again

Commit before freezing the headers

This shouldn't generally come up: under a standard flow, we don't start
sending until after the commit. But application code always finds a way.

Add a note on ActionController guide about 404

[ci skip]

Allow manually setting environment value

Given a default_scope on a parent of the current class, where that
parent is not the base class, the parent's STI condition would become
attached to the evaluated default scope, and then override the child's
own STI condition.

Instead, we can treat the STI condition as though it is a default scope,
and skip it in this situation: the scope will be merged into the base
relation, which already contains the correct STI condition.

Fixes #22426.

While the commit message (and changelog example) in
5e0b555b talked about sibling classes,
the added test had a child ignore its parent's scoping, which seems less
reasonable.

If for some reason some one is not able to set the environment from a migration this gives us an escape valve to manually set the environment for the database see https://github.com/rails/rails/pull/22967#issuecomment-170251635.

We will also fix the migration case, but this will ensure there is always a way to set the environment.

cc/ @sgrif

remove warnings from rake test

delete only unnecessary reporter

Reporter that defines its own users at the time of this process are also loaded,
to avoid them from being deleted, to delete only the specified to unnecessary reporter.

This removes the following warnings.

```
test/application/rake_test.rb:33: warning: ambiguous first argument; put parentheses or a space even after `/' operator
test/application/rake_test.rb:43: warning: ambiguous first argument; put parentheses or a space even after `/' operator
```

Extract `MySQL::{Column|TypeMetadata}` classes to the appropriate files

Pass the current locale to Inflector from the pluralize text helper.

The pluralize text helper uses the Inflector to determine the plural
form. The inflector accepts an optional parameter for the locale,
so we can pass it from the text helper to have locale-aware pluralizations
on the text helpers level.

The pluralize text helper now only accepts 2 positional arguments:
`count` and `singular`. Passing `plural` as a positional argument
is now deprecated.

Running tests with multiple line numbers

Test basic auth with symbols in password

remove mentions of legacy mysql adapter from guides

Add Example for using config_for

Update postgresql version to 9.4 for travis.