`VARIANT._get_value` cannot unpack arrays of arbitrary type

The `VARIANT._get_value` method does not unpack arrays of arbitrary type. As seen [here](https://github.com/enthought/comtypes/blob/f269c84159372799cd0f8d7b0ee23f547b0b21ec/comtypes/automation.py#L455), it is assumed that the unpacked type is in the limited `_vartype_to_ctype` dictionary. This is likely the cause behind reclosedev/pyautocad#6. The code should be expanded to handle more types.