Fix QAxBase::dynamicCallHelper check of VT_BYREF

Remember the out-parameters arguments explicitly, because the Invoke
implementation might drop the VT_BYREF bit. Still check the original
and the modified bits to be safe in case the bit is added by Invoke.

Fixes: QTBUG-13845
Change-Id: I701aeb576528aa8a429c56d9caf77db34206cb37
Done-with: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>