Description:
------------
broken after unicode patch merged

Reproduce code:
---------------
<?php
function test() {
    extract(array('a' => 1, 'ab' => 1));
    var_dump(get_defined_vars());
}
test();
?>

Expected result:
----------------
./sapi/cgi/php -dunicode_semantics=on a.php 
Content-type: text/html; charset=UTF-8
X-Powered-By: PHP/6.0.0-dev

array(2) {
  [u"a"]=>
  int(1)
  [u"ab"]=>
  int(1)
}

Actual result:
--------------
./sapi/cgi/php -dunicode_semantics=on a.php 
Content-type: text/html; charset=UTF-8
X-Powered-By: PHP/6.0.0-dev

array(2) {
  [u"a"]=>
  int(1)
  [u"a"]=>
  int(1)
}