std::string vs other strings

I can bind a function like:

const char* say_hello()
{
    return "hello";
}

or

std::string say_hello()
{
    return std::string("hello");
}

and use it with luabind easily. If I want to return another string
format like MFC's CString or Qt's QString, what do I need to do? I
grepped the source looking for something like:
  class_<std::string>("???")
    .def( ... )

I figured I would do the same thing for other string types, but I didn't
find anything. Why does std::string just seem to work?

Cory

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