Fixes "Rails 3.0 doesn't fucking work"

Add Model.select/group/order/limit/joins/conditions/preload/eager_load class methods returning a lazy relation.

  Examples :

    posts = Post.select('id).order('name') # Returns a lazy relation
    posts.each {|p| puts p.id } # Fires "select id from posts order by name"

adv_attr_accessors in ActionMailer are not sent to the views, use the mailer object if you need to access the subject, recipients, from, etc.

  Example :

    posts = Post.scoped
    posts.size # Fires "select count(*) from  posts" and returns the count
    posts.each {|p| puts p.name } # Fires "select * from posts" and loads post objects

This code was needed to work around http://redmine.ruby-lang.org/issues/show/2494. Since that bug is now closed in Ruby, we can remove it.

Instead of marking raw text in templates as safe, and then putting them through String#<< which checks if the String is safe, use safe_concat, which uses the original (internal) String#<< and leaves the safe flag as is. Results in a significant performance improvement.