Description:
------------
An exit statement inside the implementation of a custom stream filter results in a segmentation fault.

I don't have gdb on this machine, so cannot provide a stack trace. But it's quite easy to reproduce.

Test script:
---------------
<?php

class before_body_foo_filter extends php_user_filter
{
    function filter($in, $out, &$consumed, $closing)
    {
        // this exit; causes a segfault
        exit;
    }
}

stream_filter_register('before_body_foo', 'before_body_foo_filter');

$fp = fopen('php://output', 'w');
stream_filter_append($fp, 'before_body_foo', STREAM_FILTER_WRITE, 'YES');
fwrite($fp, 'hello');