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.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@900022 13f79535-47bb-0310-9956-ffa450edef68