Add `core/task_bundle.h' to the distribution.

src/Makefile.am

@@ -70,6 +70,7 @@ noinst_HEADERS = 						\
 	core/errorcheck.h					\
 	core/combined_workers.h					\
 	core/parallel_task.h					\
+	core/task_bundle.h					\
 	sched_policies/detect_combined_workers.h		\
 	sched_policies/fifo_queues.h				\
 	sched_policies/deque_queues.h				\