* w32/npth.c (struct dl): New struct.
(struct npth_impl_s): Have the struct dl at top.
(dequeue_thread, enqueue_thread): Replace old implementation.
(new_thread): Fix for the double linked list.
(free_thread): Likewise.
(struct npth_cond_s): Have the struct dl.
(npth_cond_init, npth_cond_destroy): Fix for the double linked list.
(npth_cond_signal, npth_cond_broadcast): Fix to update the list
correctly.
(npth_cond_wait, npth_cond_timedwait): Fix for the double linked list.