Android: Decide what to about screen sizes

In QScreen, we have both properties screenGeometry and availableScreenGeometry.

On Android, we set both of these to the available screen geometry, i.e. the size of the drawable surface. The reason for this is that the APIs to get the actual real screen geometry were not added before in API level 17.

We need to decide whether we should define the screen as the window we can draw into on all API versions, or if we should magically start setting the actual screen geometry when the API level is 17 or higher.