Added Orientation API to QScreen and QWindow.

QScreen now has a primary and current orientation, and a QWindow can set
its orientation as well. The current screen orientation is just a hint
to the application.

Change-Id: I4635982cfac2d16634d4edd5c6ab78e9d0ac55a4
Reviewed-on: http://codereview.qt-project.org/5988


Reviewed-by: Paul Olav Tvete <paul.tvete@nokia.com>
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>