Be slightly more forgiving about timing

[SVN r30483]

test/test_thread.cpp

@@ -41,7 +41,7 @@ void test_sleep()
 
     // Ensure it's in a range instead of checking actual equality due to time
     // lapse
-    BOOST_CHECK(in_range(xt));
+    BOOST_CHECK(in_range(xt, 2));
 }
 
 void do_test_creation()