Conflicts:
	activemodel/lib/active_model/secure_password.rb
	activerecord/lib/active_record/associations/collection_proxy.rb

This reverts commit 3fb0100e.

Update Migration Docs: Defaults for Boolean Fields

A Boolean field will accept true or false as defaults instead of 0 / 1.

added info about an error that mysql gives when rails@localhost has a password; removed reference to activerecord/test/connections, which isn't there anymore

Closes #6600

calculate errors_options one time in validate_each

errors_options is calculated for every *CHECKS* but it could be
calculated one time  because options and RESERVED_OPTIONS
not change during this cycle

Some are loaded from Base which is loaded when a model inherits from it
and some others are used in rake tasks

On reflection, it seems like a bit of a weird method to have on
ActiveRecord::Base, and it shouldn't be needed most of the time anyway.

This was requested by DHH to allow creating of one's own custom
association macros.

For example:

    module Commentable
      def has_many_comments(extra)
        has_many :comments, -> { where(:foo).merge(extra) }
      end
    end

    class Post < ActiveRecord::Base
      extend Commentable
      has_many_comments -> { where(:bar) }
    end

Remove single character body in head(:no_content) response 

Rails includes a single character body to a head(:no_content) response to work around an old Safari bug where headers were ignored if no body sent.

This patch brings the behavior slightly closer to spec if :no_content/204 is explicity requested via a head only response.

Status comparison done on symbolic and numeric values

Not returning any content when responding with head and limited to a status code that explicitly states no content will be returned - 100..199, 204, 205, 304.

Link to ActiveRecord::Serialization#to_xml for more details

Fix for digest authentication bug - issue #2301 in rails/rails

This is a private place to put those AS features that are used
by every component. Nowadays we cherry-pick individual files
wherever they are used, but that it is not worth the effort
for stuff that is going to be loaded for sure sooner or later,
like blank?, autoload, concern, etc.

Improve error handling when using partial name with hyphen. #7079

Since b6ab4417 the single quotes are
being escaped in the templates.

zero and the new value is not a string.

Before this commit this was the behavior

r = Review.find_by_issue(0)
r.issue
=> 0
r.changes
=> {}
r.issue = 0
=> 0
r.changed?
=> true
r.changes
=> {"issue"=>[0,0]}

Fixes #7237

Conflicts:
	activerecord/CHANGELOG.md