Refactor: extract back_url method to ApplicationController.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3912 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/controllers/issues_controller.rb

@@ -349,7 +349,7 @@ class IssuesController < ApplicationController
     
     @priorities = IssuePriority.all.reverse
     @statuses = IssueStatus.find(:all, :order => 'position')
-    @back = params[:back_url] || request.env['HTTP_REFERER']
+    @back = back_url
     
     render :layout => false
   end