Inside the ctor of the private data, the QObject has not yet
been associated with the data. Thus, accessing it indirectly i.e.
to setup private signal/slot connections, will trigger crashes.

Now we delay accessing this API and call an init() function manually
in the parent QObject-inheriting class.

Change-Id: I2c3ce7335c54d42af6bce87de867ee0ef197efc6
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>