oleaut32: preliminary support for VT_DISPATCH as parameters to VarAdd (and other 2-operand operations) (RESEND)

[Alex Villací­s Lasso]

This is a preliminary patch to add support for VT_DISPATCH as parameters 
to VarAdd and other arithmetic operations with variants. The tests still 
"pass" in the sense that null VT_DISPATCH as issued by the tests are 
still rejected. I post this in the hope that it will be reviewed while I 
prepare a test case.

Changelog:
* Add support for receiving of VT_DISPATCH parameters in several 
operator functions by fetching the result value, then reissuing the same 
operation on result data.

[Robert Shearman]

Alex Villací­s Lasso wrote:
> @@ -3114,6 +3155,13 @@
>            debugstr_VF(left), right, debugstr_VT(right), debugstr_VF(right),
>            result);
> - /* Handle VT_DISPATCH by recursively calling op on result of IDispatch_Invoke */
> - if (((V_VT(left) & VT_TYPEMASK) == VT_DISPATCH ||
> -
>    (V_VT(right) & VT_TYPEMASK) == VT_DISPATCH) &&
> -
>    (V_VT(left) & VT_TYPEMASK) != VT_NULL && 
> -
>    (V_VT(right) & VT_TYPEMASK) != VT_NULL) 
> -
>    return VARIANT_InvokeDispatchOp(left, right, result, VarAdd);
> - VariantInit(&lv);
>    VariantInit(&rv);
>    VariantInit(&tv);

I think you could solve this without recursion, in the same way that 
other types are coerced.