Don't include the atomic header file, if we're building a non threaded version.

This commit was SVN r15766.

opal/class/opal_atomic_lifo.h

@@ -2,7 +2,7 @@
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2006 The University of Tennessee and The University
+ * Copyright (c) 2004-2007 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -21,7 +21,10 @@
 
 #include "opal_config.h"
 #include "opal/class/opal_list.h"
+
+#if OMPI_HAVE_THREAD_SUPPORT
 #include "opal/sys/atomic.h"
+#endif  /* OMPI_HAVE_THREAD_SUPPORT */
 
 #if defined(c_plusplus) || defined(__cplusplus)
 extern "C" {