Merge r900022 from trunk.

Turn static function get_server_name_for_url() into public function
ap_get_server_name_for_url() and use it where appropriate. This fixes
mod_rewrite generating invalid URLs for redirects to IPv6 literal addresses.

Committed by: sf
Reviewed by: jailletc36, ylavic, rjung
Backported by: ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1678714 13f79535-47bb-0310-9956-ffa450edef68