Method spawn_root_and_wait

benchmarks/tbb/task.h:720–722

Spawn task allocated by allocate_root, wait for it to complete, and deallocate it.

    //! Spawn task allocated by allocate_root, wait for it to complete, and deallocate it.
    static void spawn_root_and_wait( task& root ) {
        root.prefix().owner->spawn_root_and_wait( root, root.prefix().next );
    }

    //! Spawn root tasks on list and wait for all of them to finish.
    /** If there are more tasks than worker threads, the tasks are spawned in