- stretch data pixbuf to output using raw force, i.e. just scaling to
  image.w, image.h
- always draw to pixmaps pixelated
- offer the full set of Gwyddion interpolations when drawing to pixmaps


git-svn-id: svn://svn.code.sf.net/p/gwyddion/code/trunk/gwyddion@16693 25697fe4-d644-49b8-9d30-be5465f2adf3