Add tests for testing the SCARY-ness of iterators

test/Jamfile.v2

@@ -1,5 +1,6 @@
 
 # Copyright 2006-2008 Daniel James.
+# Copyright 2022 Christian Mazakas
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
@@ -77,6 +78,7 @@ test-suite unordered
         [ run unordered/contains_tests.cpp ]
         [ run unordered/mix_policy.cpp ]
         [ run unordered/erase_if.cpp ]
+        [ run unordered/scary_tests.cpp ]
 
         [ run unordered/compile_set.cpp : :
             : <define>BOOST_UNORDERED_USE_MOVE