Summary: Callback event loop was busted.

Summary: Callback event loop was busted.
Keywords:

The comms callback event loop was not dereferencing the dlink_node correctly, leading to comparing the sequence number to a pointer. Once again, typecasts leads to bugs :[.
* Increment sequence number on each loop.
* Compare to the event's record sequence number.
* Add a virtual destructor to CommCallbackData to remove some (spurious) warnings that apply to the synthetic constructor under -some- gcc's.