Unordred: Implement propagate_on_container_swap.

[SVN r73680]

test/unordered/Jamfile.v2

@@ -43,5 +43,5 @@ test-suite unordered
         [ run load_factor_tests.cpp ]
         [ run rehash_tests.cpp ]
         [ run equality_tests.cpp ]
-        [ run swap_tests.cpp : : : <define>BOOST_UNORDERED_SWAP_METHOD=2 ]
+        [ run swap_tests.cpp ]
     ;