Prevent clash with Rails 3 Query module.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@7899 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/query.rb

@@ -352,7 +352,7 @@ class Query < ActiveRecord::Base
 
   def available_columns
     return @available_columns if @available_columns
-    @available_columns = Query.available_columns
+    @available_columns = ::Query.available_columns
     @available_columns += (project ?
                             project.all_issue_custom_fields :
                             IssueCustomField.find(:all)