Added limited emplace() for older compilers

test/Jamfile.v2

@@ -25,6 +25,7 @@ import testing ;
     [ run optional_test_equals_none.cpp ]
     [ run optional_test_value_access.cpp ]
     [ run optional_test_emplace.cpp ]
+    [ run optional_test_minimum_requirements.cpp ]
     [ compile-fail optional_test_fail1.cpp ]
     [ compile-fail optional_test_fail3a.cpp ]
     [ compile-fail optional_test_fail3b.cpp ]