make webfinger work properly if owncloud is installed in a subdirectory

apps/user_webfinger/webfinger.php

@@ -4,7 +4,14 @@ if($_SERVER['SCRIPT_NAME'] == '/.well-known/webfinger.php') {
 } else {
 	header('Please-first: activate');
 }
-header("Content-Type: application/xml+xrd");
+// header("Content-Type: application/xml+xrd");
+
+// calculate the documentroot
+// modified version of the one in lib/base.php that takes the .well-known symlink into account
+$DOCUMENTROOT=realpath($_SERVER['DOCUMENT_ROOT']);
+$SERVERROOT=str_replace("\\",'/',dirname(dirname(dirname(dirname(__FILE__)))));
+$SUBURI=substr(realpath($_SERVER["SCRIPT_FILENAME"]),strlen($SERVERROOT));
+$WEBROOT=substr($SUBURI,0,-34);
 
 if($_GET['q']) {
 	$bits = explode('@', $_GET['q']);
@@ -20,5 +27,5 @@ echo "<";
 ?xml version="1.0" encoding="UTF-8"?>
 <XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0" xmlns:hm="http://host-meta.net/xrd/1.0">
 	<hm:Host xmlns="http://host-meta.net/xrd/1.0"><?php echo $_SERVER['SERVER_NAME'] ?></hm:Host>
-	<Link rel="http://unhosted.org/spec/dav/0.1" href="http<?php echo ($_SERVER['HTTPS']?'s':''); ?>://<?php echo $_SERVER['SERVER_NAME'] ?>/apps/remoteStorage/compat.php/<?php echo $userName ?>/remoteStorage/" />
+	<Link rel="http://unhosted.org/spec/dav/0.1" href="http<?php echo ($_SERVER['HTTPS']?'s':''); ?>://<?php echo $_SERVER['SERVER_NAME'].$WEBROOT ?>/apps/remoteStorage/compat.php/<?php echo $userName ?>/remoteStorage/" />
 </XRD>