Add a debug proxy style that wraps around an existing style and outputs
the parameters and return values of its function calls, for debugging
QStyle.
Task-number: QTBUG-47084
Task-number: QTBUG-45055
Change-Id: I638618e83bbac8ca4fdce31441bf4c913e911154
Reviewed-by: Andy Shaw <andy.shaw@theqtcompany.com>