Fixed an inclusion order bug between the shared_ptr_thread_safe and thread_pool files.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403151

dlib/smart_pointers/shared_ptr_thread_safe.h

@@ -9,7 +9,7 @@
 #include <string>       // for the exceptions
 #include "../algs.h"
 #include "shared_ptr_thread_safe_abstract.h"
-#include "../threads.h"
+#include "../threads/threads_kernel.h"
 
 
 namespace dlib