Replace a call to changes with its code from AR::Dirty. #422

acts_as_journalized called changes as per ActiveRecord::Dirty 
(see http://ar.rubyonrails.org/classes/ActiveRecord/Dirty.html#M000291), 
the journalized model Changeset :has_many changes though, which 
made the call return a list of associated objects instead of the 
intended list of changed attributes. Replaced changes with the code
from AR::Dirty to work around that.

vendor/plugins/acts_as_journalized/lib/redmine/acts/journalized/changes.rb

@@ -88,7 +88,7 @@ module Redmine::Acts::Journalized
         # creation. Incremental changes are reset when the record is saved because they represent
         # a subset of the dirty attribute changes, which are reset upon save.
         def incremental_journal_changes
-          changes.slice(*journaled_columns)
+          changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h }.slice(*journaled_columns)
         end
 
         # Simply resets the cumulative changes after journal creation.