Some data was never serialized (styleName, hintingPreference) and
some was incorrectly serialized (styleStrategy). This change also adds
auto tests for every applicable QDataStream version.
[ChangeLog][QtGui][QFont] QFont now serializes its data properly,
without any data loss.
Task-number: QTBUG-22814
Task-number: QTBUG-22946
Change-Id: I34e61b10662b7ad6c57054dacc7e1f522f5b5c5d
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>