quick fixing this require_once.

On windows the wrong file will be required: lib/archive/tar.php and not Archive/Tar.php.

Best would be to rename the lib/archive/tar.php or put it into a different folder

lib/archive/tar.php

@@ -6,7 +6,7 @@
  * See the COPYING-README file.
  */
 
-require_once 'Archive/Tar.php';
+require_once OC::$THIRDPARTYROOT . '/3rdparty/Archive/Tar.php';
 
 class OC_Archive_TAR extends OC_Archive{
 	const PLAIN=0;