* workqueue-internal.h (Workqueue_threader::should_cancel_thread):

	* workqueue-internal.h (Workqueue_threader::should_cancel_thread):
	Add thread_number parameter.
	(Workqueue_threader_threadpool::should_cancel_thread): Likewise.
	* workqueue-threads.cc
	(Workqueue_threader_threadpool::should_cancel_thread): Cancel
	current thread if its thread number is greater than desired thread
	count.
	* workqueue.cc (Workqueue_threader_single::should_cancel_thread):
	Add thread_number parameter.
	(Workqueue::should_cancel_thread): Likewise.
	(Workqueue::find_runnable_or_wait): Pass thread_number to
	should_cancel_thread.
	* workqueue.h (Workqueue::should_cancel_thread): Add thread_number
	parameter.