Backwards compatibility fixes for relative_url_root

* Make the old deprecated relative_url_root still set the value as it's still used by mongrel
* Set the default from the ENV value when the file is required, not at runtime.

actionpack/lib/action_controller/base.rb

@@ -364,11 +364,8 @@ class Base
     # If you are deploying to a subdirectory, you will need to set
     # <tt>config.action_controller.relative_url_root</tt>
     # This defaults to ENV['RAILS_RELATIVE_URL_ROOT']
-    cattr_writer :relative_url_root
-
-    def self.relative_url_root
-      @@relative_url_root || ENV['RAILS_RELATIVE_URL_ROOT']
-    end
+    cattr_accessor :relative_url_root
+    self.relative_url_root = ENV['RAILS_RELATIVE_URL_ROOT']
 
     # Holds the request object that's primarily used to get environment variables through access like
     # <tt>request.env["REQUEST_URI"]</tt>.

actionpack/lib/action_controller/request.rb

@@ -9,10 +9,11 @@ module ActionController
   class AbstractRequest
     extend ActiveSupport::Memoizable
 
-    def self.relative_url_root=(*args)
+    def self.relative_url_root=(relative_url_root)
       ActiveSupport::Deprecation.warn(
         "ActionController::AbstractRequest.relative_url_root= has been renamed." +
         "You can now set it with config.action_controller.relative_url_root=", caller)
+      ActionController::base.relative_url_root=relative_url_root
     end
 
     HTTP_METHODS = %w(get head put post delete options)