[Development] Updating "Serializing Qt Data Types" documentation

[Harri Porten]

On Wed, 24 Oct 2012, Jedrzej Nowacki wrote:

>  I added that tests durring Qt5 development, sadly streaming was never tested
> with older versions. What is the bug, can I help somehow? Is it only Qt5 or
> Qt4 too?

We found the reason now:

   https://bugreports.qt-project.org/browse/QTBUG-27700

Streaming of invalid QVariants with Qt 5 for older versions does not work 
anymore. The test attached to above report isn't really elegant, yet. 
We'll improve upon that and try to submit a patch. Stay tuned.

Harri.