fix defect in semaphore implementation which caused application hang …

…at exit time, because not all worker threads get woken up when task semaphore is repeatedly posted (to wake them up) after setting the stopping flag in the thread pool

IlmBase/IlmThread/IlmThreadSemaphorePosixCompat.cpp

@@ -126,7 +126,16 @@ Semaphore::post ()
 
     if (_semaphore.numWaiting > 0)
     {
-        if (int error = ::pthread_cond_signal (&_semaphore.nonZero))
+        int error;
+        if (_semaphore.numWaiting > 1 && _semaphore.count > 1)
+        {
+            error =  ::pthread_cond_broadcast (&_semaphore.nonZero);
+        }
+        else
+        {
+            error = ::pthread_cond_signal (&_semaphore.nonZero);
+        }
+        if (error)
         {
             ::pthread_mutex_unlock (&_semaphore.mutex);