qvfb display offset by one pixel in 270 degree rotation

Tested using qvfb built from //depot/qt-git/4.4@668f9de15f3ae73244ef2d380d0389247d2a4598 (Fri Dec 19 15:25:58 2008 +0100).

When qvfb is rotated by 270 degrees, a single row of unpainted (i.e. random) pixels is shown at the top of the framebuffer display. This does not happen in the other three rotations.

This bug happens regardless of whether qvfb is using a skin, and regardless of whether an application is running inside the framebuffer, as shown in the two attached screenshots. The first shows Qtopia running in qvfb with the Greenphone skin. The second shows qvfb with no skin and no application, rotated by 270 degrees via the View menu.