Description:
------------
extract() fail to treats keys as variable names when a key contains ASCII characters from 127 through 255 (0x7f-0xff).

Reproduce code:
---------------
<?php
    $?t? = "#";
    $a = array('?t?' => '---');

    echo extract($a); /* Failure: return 0 instead of 1 */

    echo $?t?; /* Failure consequence, print '#' instead of '---' */
?>

Expected result:
----------------
1---

Actual result:
--------------
0#