pluto: Added a generic event queue.

This allows to easily execute arbitrary callbacks in the context of the pluto
main thread (e.g. in order to synchronize with threads from the thread-pool).

src/pluto/pluto.h

@@ -31,6 +31,7 @@
 
 typedef struct pluto_t pluto_t;
 
+#include <event_queue.h>
 #include <xauth/xauth_manager.h>
 
 #include <library.h>
@@ -40,10 +41,16 @@ typedef struct pluto_t pluto_t;
  */
 struct pluto_t {
 
+	/**
+	 * event queue (callbacks, executed by the pluto main thread)
+	 */
+	event_queue_t *events;
+
 	/**
 	 * manager for payload attributes
 	 */
 	xauth_manager_t *xauth;
+
 };
 
 /**