Description:
------------
Double-flock()ing a file with different handles crashes. 

Reproduce code:
---------------
<?php
$fp = fopen('generic-textfile.txt', 'w');
flock($fp, LOCK_EX);
$fp2 = fopen('generic-textfile.txt', 'w');
flock($fp2, LOCK_EX);
echo 'Dun!';
?>

Expected result:
----------------
Dun!

Actual result:
--------------
Nothing