Provide a way of getting complex properties that have no annotations from the remote side

I wanted to read the "KnownFilesystems" parameter of org.freedesktop.UDisks, but obviosly QtDBus can not handle this complex property.

Attached a test main.cpp, which is an example for the problem. Compiled with QT += testlib dbus using Qt 4.7, the following Errors occur:
QWARN : tst_UDisksProperties::complexProperties() QDBusAbstractInterface:
type QDBusRawType<0x6128737362626275626262626262626229>* must be registered
with QtDBus before it can be used to read property
org.freedesktop.UDisks.KnownFilesystems
QDEBUG : tst_UDisksProperties::complexProperties() QVariant(, )
QDEBUG : tst_UDisksProperties::complexProperties()
QDBusError("org.freedesktop.DBus.Error.Failed", "Unregistered type
QDBusRawType<0x6128737362626275626262626262626229>* cannot be handled")