Thumbnail generation for Unicode requires some changes:
- 72x72 images (exact, not just fit within that frame)
- custom prefix ending in underscore
- images for unsupported flags
The default build doesn't support some flags by default, since they
are not wanted by Android. For the thumbnail list these images need
to be provided, so we alias them to the unknown flag images as that's
what would show for them. It's probably a good idea to list these
explicitly anyway, other tools could use this information.
Doug Felt