Made the timer test a little more robust.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403689

dlib/test/timer.cpp

@@ -78,7 +78,7 @@ namespace
             dlib::uint64 cur_time = h.ts.get_timestamp();
 
             // make sure the action function has been called recently
-            DLIB_TEST_MSG((cur_time-h.timestamp)/1000 < 10, (cur_time-h.timestamp)/1000);
+            DLIB_TEST_MSG((cur_time-h.timestamp)/1000 < 30, (cur_time-h.timestamp)/1000);
 
         }
     }