Introduce DaedalusVm::top_is_reference

[Try]

This PR adds a function to inspect top record of the stack without removing it.

Need to add this one, in order to support _@ in ikarus.
Sometimes argument for _@ can be a reference, such as:

int MAXCHAR;
...
CALL_INTPARAM(_@(MAXCHAR));

in this case opengothic will map them into the "Ikarus memory".

and sometimes _@ may take an instance, that decays into an integer, such as:

func int LIST_END(var int LIST) {
    var ZCLIST L;
    if (!(LIST)) {
        _LIST_ERRPTR("End");
        return 0;
    };
    L = _^(LIST);
    WHILE(L.NEXT);
    L = _^(L.NEXT);
    END;
    return _@(10426);
}

In that case 10426 is ID of the symbol LIST_END.L, and instance associated with it need to be returned by pointer.

[lmichaelis]

Looks good!