merge this to 2.0.45-dev:

 *) Keep the subrequest filter in place when a subrequest is
    redirected.  PR 15423.  [Jeff Trawick]


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@98991 13f79535-47bb-0310-9956-ffa450edef68