Description:
------------
If an event's a callback is a method of the object, which holds a reference to 
this event, the object leaks after both the event and the object have been 
nulled.

The test script performs 3 tests:
 - test 1 holds the event as a global variable, and the callback object is 
released as expected;
 - test 2 holds the event as a property of another object, and the callback 
object is released as expected;
 - test 3 holds the event as a property of the same object, which is used for the 
callback, and the object does not get released.

I guess the event leaks too, but I didn't check.

I'm not sure if it's pecl-libevent's or PHP Garbage Collector's bug, but I 
suppose that behaviour is not something one should expect.

The workaround is to explicitly break the reference from the object to the event.


Test script:
---------------
https://gist.github.com/5lava/62629f3d66c9124d2877

Expected result:
----------------
destruct 1
==== THE END of test 1 ====
destruct 3
destruct 2
==== THE END of test 2 ====
destruct 4
==== THE END of test 3 ====


Actual result:
--------------
destruct 1
==== THE END of test 1 ====
destruct 3
destruct 2
==== THE END of test 2 ====
==== THE END of test 3 ====
destruct 4