remove ruby 1.8 checking in constantize method

Fix rails/generators/base.rb documentation for hook_for

is one benefit of choosing composition over inheritance.

allow reorder to affect eager loading correctly

refactor AR::PredicateBuilder.build_from_hash

Rails template creation issue

This reverts commit 90df0d4f, reversing
changes made to 5e6fc81d.

Reason: build breakage

This is the 'top level' connection, inherited by any models that include
ActiveRecord::Model or inherit from ActiveRecord::Base.

The problem: We need to be able to specify configuration in a way that
can be inherited to models that include ActiveRecord::Model. So it is
no longer sufficient to put 'top level' config on ActiveRecord::Base,
but we do want configuration specified on ActiveRecord::Base and
descendants to continue to work.

So we need something like class_attribute that can be defined on a
module but that is inherited when ActiveRecord::Model is included.

The solution: added ActiveModel::Configuration module which provides a
config_attribute macro. It's a bit specific hence I am not putting this
in Active Support or making it a 'public API' at present.

deprecate Base64.encode64s from AS

Further simplify singleton_class checking in class_attribute

Refactor AS::Callbacks

Extracted `__reset_runner` from `__define_runner`
And call it in proper places

AR#where with an Array of 2 elements including a nil

Fix a fixtures test case with table prefix/suffix

Fixed a bug in fixtures.rb where the table name was incorrectly inferred from the fixture path which was ambiguously called "table_name" but was also used as the fixture name.
Now, the "correct" table name is taken from an instance variable.

was "WHERE foo IN (1) OR foo IS NULL" before

Revert "This conditions is required to work with database create task.