Description:
------------
HTTP proxing (after 5.1.0) works only if request_fulluri is set to true.
And there is no documentation about this.

Reproduce code:
---------------
$context = stream_context_create(
    array('http'=>
        array(
           'proxy' => 'tcp://proxy.domain.com:3128/',
           //'request_fulluri' => true,//Works if uncommented
        )
    )
);
$data = file_get_contents('http://google.com/', false, $context);
var_export($data);


Expected result:
----------------
+

Actual result:
--------------
Warning: file_get_contents(http://google.com/): failed to open stream: HTTP request failed! HTTP/1.0 400 Bad Request
 in http_proxy_bug.php on line 10
-