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/daemon/worker.h

@@ -61,6 +61,7 @@ struct ub_randstate;
 struct regional;
 struct tube;
 struct daemon_remote;
+struct query_info;
 
 /** worker commands */
 enum worker_commands {
@@ -84,7 +85,7 @@ struct worker {
 	/** global shared daemon structure */
 	struct daemon* daemon;
 	/** thread id */
-	ub_thread_t thr_id;
+	ub_thread_type thr_id;
 	/** pipe, for commands for this worker */
 	struct tube* cmd;
 	/** the event base this worker works with */