Changes for making strings safe to use as output parameters

There are two approaches here. Create the string with a private allocated buffer.

    cScrStr str(0);
    pEngineSrv->ConfigGetRaw("foo", str);
    str->Free();

Or reset the string to `NULL`.

    cScrStr str;
    str->MakeNull();
    pEngineSrv->ConfigGetRaw("foo", str);
    str->Free();

Setting to `NULL` is quick and dirty. But allocating a buffer has the side-effect that you can const-cast the pointer if you want to write to it.

    cScrStr str(64);
    snprintf(const_cast<char*>(static_cast<const char*>(str)), 64, "%f", value);

But if you're going to do that a lot, you should be using `cAnsiStr`.

More testing needs to be done to see if either of these are viable solutions.