Silenced GCC 4.0.1 warning (patch supplied by Euan)

<http://thread.gmane.org/gmane.comp.lib.boost.devel/171071>

[SVN r43274]

libs/statechart

@@ -1 +1 @@
-Subproject commit a3d35138a3d471a1a5d64a2e3b9e11399ff4a76a
+Subproject commit ce4ee68b568ed3404062d6e46f635322fabe9b74