eventlog: Repost initialisation events when eventlog restarts

If startEventlog is called after the program has already started running then quite a few useful events are missing from the eventlog because they are only posted when the program starts. This patch adds a mechanism to declare that an event should be reposted everytime the startEventlog function is called.

Now in EventLog.c there is a global list of functions called eventlog_header_funcs which stores a list of functions which should be called everytime the eventlog starts.

When calling postInitEvent, the event will not only be immediately posted to the eventlog but also added to the global list.

When startEventLog is called, the list is traversed and the events reposted.