- The condition variable implementation "lost" a signal to
  WaitOnSingleObject when a semaphore was released.
- The signal could be consumed by a new call to pthread_cond_wait
  before all waiting threads had awoken.
- The new implementation of pthread_cond_* uses events
  instead of semaphores. It also uses an extra lock to protect entry
  into new cond wait before the broadcast has finished.