Determine whether video graphics view window fading can be re-enabled on future Symbian devices

The cause of QTMOBILITY-1305 was found to be lack of graphics memory on devices using the IVE3, causing window fading to fail. The workaround implemented for this bug was therefore to disable fading on both the video window and the viewport window.

On future devices, with more graphics memory, it may be possible to re-enable window fading. Ideally, the decision on whether to disable fading would be done on the basis of the result of a platform API call; alternatively, the approach taken in QTBUG-18024 (querying the GPU chipset ID and hard-coding a lookup table for the capabilities of each chip) could be used.