Added explicit test with the alias 'test_iso' to run tests for macro expansion for the various C++ standards.

test/Jamfile.v2

@@ -262,3 +262,8 @@ alias test_clang_cuda
   ;
 
 explicit test_clang_cuda ;
+
+alias test_iso
+   :   
+        [ run cpp_standard.cpp ]
+  ;