Added support for maintaining URL anchors/fragments after security redirect

Anchors/fragments are lost across redirects, as the server-side handler of the form post ignores the client-side anchor, unless appended to the form POST url.  See https://jira.springsource.org/browse/SEC-1067 for more details.  This feature is needed if you want a CAS-authenticated application to be able to use anchors/fragments when bookmarking.  If the user has a bookmark with an anchor/fragment in it and is redirected to the login page when attempting to navigate to the link with the anchor, the anchor will be lost upon redirect without this patch.