Ensure that wxBitmapBundleImplSet and wxBitmapBundleImplRC use the same logic for actually selecting the bitmap to upscale, and not just for deciding the size that it must have, too. No real changes, but this should make impossible for these functions to diverge once again -- and also make it simpler to reuse the same logic in any other wxBitmapBundleImpl-derived classes in the future.