Remove event_base.evsigbase; nothing used it.

event-internal.h

@@ -177,8 +177,6 @@ struct event_base {
 	/** Function pointers used to describe the backend that this event_base
 	 * uses for signals */
 	const struct eventop *evsigsel;
-	/** Pointer to signal backend-specific data*/
-	void *evsigbase;
 	/** Data to implement the common signal handelr code. */
 	struct evsig_info sig;
 

signal.c

@@ -204,7 +204,6 @@ evsig_init(struct event_base *base)
 	base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;
 
 	base->evsigsel = &evsigops;
-	base->evsigbase = &base->sig;
 
 	return 0;
 }