Based on mod_event_socket.

- create listeners
- parse sccp header (length, reserved, type)
- don't listen to reloadxml event, as we don't reload listeners
- listen to heartbeat event to expire listeners

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@16747 d0543943-73ff-0310-b7d9-9358b9ac24b2