Applied Patch from https://rails.lighthouseapp.com/projects/8994/tickets/5577-suport-from-tsvector-data-type-in-postgresql

Bring back support for passing a callable object to the default_scope macro. You can also just use a block.

Un-deprecate using 'default_scope' as a macro, but if you are calling the macro multiple times that will give deprecation warnings, and in 3.2 we will simply overwrite the default scope when you call the macro multiple times.

Fix test_load_save in test/cases/binary_test.rb (thanks @tenderlove for actually working out how to fix it)

Bring back some bits of documentation for scopes which were removed as part of the reversion in 256b363e

Revert "Deprecate defining scopes with a callable (lambda, proc, etc) via the scope class method. Just define a class method yourself instead."

This reverts commit f0e198bf.

Conflicts:

	activerecord/test/models/post.rb

Return nil from read_attribute(:foo) if 'foo' is not present in the @attributes hash, but the _foo method has been defined. This brings the behaviour into line with the 3-0-stable branch and the master branch before 93641ed6 (there were previously no assertions about this which is why the change slipped through). Note that actually calling the 'foo' method will still raise an error if the attribute is not present.

Undo performances regressions I introduced in bbe0a507 and add test for an edge case. Add comments to explain the intent of the code.

Remove unnecessary code from define_read_method and add assertion to make sure the underscored version is actually generated

Extract the constraint-building for joins in JoinAssociation into a separate method to make it easy to change/override (requested by Ernie Miller so that MetaWhere can add to it easily)

After a long list of discussion about the performance problem from using varargs and the reason that we can't find a great pair for it, it would be best to remove support for it for now.

It will come back if we can find a good pair for it. For now, Bon Voyage, `#among?`.

Deprecate defining scopes with a callable (lambda, proc, etc) via the scope class method. Just define a class method yourself instead.

Evaluate default scopes at the last possible moment in order to avoid problems with default scopes getting included into other scopes and then being unable to remove the default part via unscoped.

Deprecated support for passing hashes and relations to default_scope, in favour of defining a 'default_scope' class method in the model. See the CHANGELOG for more details.

Removing the scope-caching which happens on association proxies, because the query is already cached by the query cacher. For formalised proof see http://www.youtube.com/watch?v=wDefXLb-FDs