Description:
------------
When using ob_gzhandler with PHP 5.4.0+, PHP will emit warnings after flushing 
more than once (it looks like it's trying to modify headers on each flush).

This problem didn't exist in PHP 5.3.


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

ob_start('ob_gzhandler');

echo "PHP VERSION ".phpversion()."\n";
ob_flush();
flush();

echo "This is confusing:\n";
ob_flush();
flush();


Expected result:
----------------
PHP VERSION 5.5.0-dev
This is confusing:

Actual result:
--------------
PHP VERSION 5.5.0-dev
This is confusing:

Warning: Cannot modify header information - headers already sent by (output 
started at php-src/moo.php:6) in php-src/moo.php on line 10