Upgrade unbound library

These files were pulled from the 1.6.3 release tarball.

This new version builds against OpenSSL version 1.1 which will be
the default in the new Debian Stable which is due to be released
RealSoonNow (tm).

external/unbound/util/mini_event.h

@@ -96,7 +96,7 @@
 struct event_base
 {
 	/** sorted by timeout (absolute), ptr */
-	rbtree_t* times;
+	rbtree_type* times;
 	/** array of 0 - maxfd of ptr to event for it */
 	struct event** fds;
 	/** max fd in use */
@@ -128,7 +128,7 @@ struct event_base
  */
 struct event {
 	/** node in timeout rbtree */
-	rbnode_t node;
+	rbnode_type node;
 	/** is event already added */
 	int added;