Use std::bind instead of using function outside class

[theod]

In many place I use to do this :

class AnyClass { ... friend TTErr TT_EXTENSION_EXPORT aCallbackFunctionOutsideTheClass(const TTValue& baton, const TTValue& data);

};

TTErr TT_EXTENSION_EXPORT aCallbackFunctionOutsideTheClass(const TTValue& baton, const TTValue& data);

but @jcelerier told me it is possible to pass directly a method of a class using std::bind.