I upsampled them in gimp using the "None" filter and manually cleaned up
the outline. The drop shadow is just upsampled using "None" and looks a
bit rough -- someone who knows how to do this either has to re-create
the shadow on the 2x bitmaps, or we need to remove the shadow from the
resource and render it in code at some point. Still, looks a lot better
than with the upsampled 1x bitmaps.
