Update Rails, rails_xss and Bundler

Update Bundler to 1.0.15.
Update Rails to 2.3.12.
Update rails_xss plugin.

The latter two were the
source of a considerable
amount of grief, as rails_xss
is now MUCH stricter about what
string methods can be used.

Also made it possible to use
rake 0.9.x with Instiki. But
you probably REALLY want to use

 ruby bundle exec rake ...

instead of just saying

 rake ....

vendor/rails/actionpack/lib/action_controller/request.rb

@@ -446,7 +446,9 @@ EOM
     end
 
     def reset_session
-      session.destroy if session
+      # session may be a hash, if so, we do not want to call destroy
+      # fixes issue 6440
+      session.destroy if session and session.respond_to?(:destroy)
       self.session = {}
     end
 

vendor/rails/actionpack/lib/action_controller/session/abstract_store.rb

@@ -196,6 +196,7 @@ module ActionController
 
           if (request_cookies.nil? || request_cookies[@key] != sid) || options[:expire_after]
             cookie = {:value => sid}
+            cookie[:expires] = Time.now + options[:expire_after] if options[:expire_after]
             Rack::Utils.set_cookie_header!(response[1], @key, cookie.merge(options))
           end
         end