Limit the size of queues

In various parts of Openfire, queues are in use to (temporarily) store data (often Packets). If a bug is introduced where those queues aren't emptied, a memory leak occurs.

Queues should all get a defined capacity, smaller than the maximum integer value. The capacity should be set in such a way that it will not be reached under extreme, but valid circumstances.

If a queue reaches capacity (runtime) exceptions will be thrown and logged, which will make the source of the problem very visible.