preparation callbacks are gone

Lots of plugins use config.to_prepare. It looks like we're supposed to add callback hooks to ActionDispatch now. Rails::Configuration should probably do that for us.

Here's what the OpenIDAuthentication plugin's init.rb looks like in my edit:

init_block = lambda do
  OpenID::Util.logger = Rails.logger
  ActionController::Base.send :include, OpenIdAuthentication
end

if defined? ActionDispatch::Callbacks
  ActionDispatch::Callbacks.before_dispatch(&init_block)
else
  config.to_prepare(&init_block)
end