Transformation: Added BBitmap test
Painter: Complete bitmap clipping and transformation

 * Turn off optimized code-paths when an alpha mask is set. The generic
   path already included the alpha-mask version of the AGG pipeline.
 * Add transformation to generic bitmap rendering. (It already worked
   with a transformation, so there is no slow down compared to before,
   only now it also includes the transformation set via BView::SetTransform())