Description:
------------
The regexp used for validating URLs rejects umlaut domains -- umlaut domains are legal nowadays, so filter should support them... since IE6 does NOT support them, I'd suggest adding a new flag, like FILTER_FLAG_ALLOW_UMLAUTS.

Reproduce code:
---------------
<?php
// Dom?ne: German for domain
// dom?ne.de actually exists
$url = 'http://www.dom?ne.de/';
var_dump(filter_var($url, FILTER_VALIDATE_URL));
?>

Expected result:
----------------
string(21) "http://www.dom?ne.de/"

Actual result:
--------------
bool(false)