Use unified and clean formatting in CHANGELOGS. [ci skip]

Simpler, thanks to @rubys for the hint.

refactor order hash test; remove unused method param

Conflicts:
	guides/source/action_mailer_basics.md

Unabbreviate AP to ActionPack [ci skip]

Revert "added details to section 4.1.2 of the Asset Pipeline guide, describing how to configure Apache to serve the gzipped version of the precompiled assets"

This reverts commit aec466e7.

Reason: We're not sure about the correctness and won't want to document
something like this with doubts.

initialize instead of assert to fix warning

[ci skip]

Address ORA-00979: not a GROUP BY expression error

Cleanup statement cache test

warning: `*' interpreted as argument prefix

Editorial pass over generated Gemfile

* When run with default options, no repeated blank lines
* Every gem has a comment, perhaps a generic one, but a comment nonetheless
* Most comments used to start with "Use", some with "To use" => made consistent

Statement cache

Conflicts:
	activerecord/CHANGELOG.md

Simple improvements

This reverts commit 9bf1a0db, reversing
changes made to fed97091.

Conflicts:
	activerecord/test/cases/transaction_callbacks_test.rb

Reason: This fix introduces another issue described at #8937, so we are
reverting it to restore the behavior of 3-2-stable.

We will fix both issues when we come out with a better solution

While merging relations preserve context for joins

Fixes #3002. Also see #5494.

```
class Comment < ActiveRecord::Base
  belongs_to :post
end

class Author < ActiveRecord::Base
  has_many :posts
end

class Post < ActiveRecord::Base
  belongs_to :author
  has_many :comments
end
```

`Comment.joins(:post).merge(Post.joins(:author).merge(Author.where(:name => "Joe Blogs"))).all` would
fail with `ActiveRecord::ConfigurationError: Association named 'author' was not found on Comment`.

It is failing because `all` is being called on relation which looks like this after all the merging:
`{:joins=>[:post, :author], :where=>[#<Arel::Nodes::Equality: ....}`. In this relation all the context that
`Post` was joined with `Author` is lost and hence the error that `author` was not found on `Comment`.

Ths solution is to build JoinAssociation when two relations with join information are being merged. And later
while building the arel use the  previously built `JoinAssociation` record in `JoinDependency#graft` to
build the right from clause.

Thanks to Jared Armstrong (https://github.com/armstrjare) for most of the work. I ported it to make it
compatible with new code base.

This reverts commit fa3ef8e8, reversing
changes made to e0af93dd.

Reason: Routes, Active Record and the rendering stack should not depend
on the default locale

Searching for rails executable correctly

 * Current logic of finding Rails executable in parent directory is
   not returning full path of executable if it is found in one of the
   parent directories
 * To compensate for this, we have to call exec_app_rails recursively
   until the executable is found or we cant do 'chdir' anymore
 * This solution finds the correct executable path from parent
   directory(s) recursively

Using public send instead of send for the PerThreadRegistry module.

Prevents you from accidentally calling a protected method.

Removed unused setup