Drawing a RenderedImage with premultiplied alpha using
Graphics2D.drawRenderedImage results in garbage. The image data is
extracted as a Raster which is then wrapped into a BufferedImage. However,
the 'isAlphaPremultiplied' flag of the BufferedImage constructor is
always set to false instead of being set to the same value as in the
original image's ColorModel.

The existing regression test sun/java2d/SunGrphics2D/DrawRenderedImageTest
will be extended to display images with and without premultipled alpha.