Description:
------------
There is a memory leak when using the get method on a queue in a while loop when 
there are no messages in the queue. I was using version 1.0.1 of the amqp 
extension. There is a simple fix for this that I found. Before line 207 in 
amqp_queue.c where it returns AMQP_READ_NO_MESSAGES, release the memory allocated 
for the envelopeZval with:

"zval_dtor(envelopeZval);"

This should fix the leak when no messages are in queue and prevent the script's 
memory footprint from growing.

Test script:
---------------
#!/usr/bin/php -q
<?php
// This assumes you have an exchange named 'exchange.hello' set up.
$connection = new AMQPConnection(); $connection->connect();
$channel = new AMQPChannel($connection);
$q = new AMQPQueue($channel); $q->setName('queue.hello'); $q->declare();
$start = time();
while (true)
{
	$msg = $q->get(AMQP_AUTOACK);
	if (time() - $start > 2) // print out memory usage every 2 secs.
	{
		$start = time();
		echo memory_get_usage() . "\n";
	}
}
$connection->disconnect(); // disconnect

Expected result:
----------------
I expect the memory usage amount to remain constant when no messages are in the 
queue to process.

Actual result:
--------------
The memory usage value grows and grows until I run out of memory.