Change function signature to void*

There might be vaious EventHandler so we accept every of these
and cast accordingly...

@@ -35,7 +35,7 @@ TR_CLASS(TR_EventHandler);
 
 #include "tr/event_dispatcher.h"
 
-typedef TR_EventDone (* TR_EventMethod_fptr)(TR_EventHandler, TR_Event);
+typedef TR_EventDone (* TR_EventMethod_fptr)(void *, TR_Event);
 
 TR_CLASS(TR_EventHandler) {
 	TR_EventDispatcher dispatcher[10];