Currently, if you wish to include an image file inline with your documentation, you use a "link:" tag with
the path to that file relative to the output directory. This usually means that the image file itself is left outside
of the output directory.

If you want to zip up the documentation and send it somewhere, say a web server, you can't just include the directory
rdoc creates, you have to also include the image files, in whatever directory rdoc thinks they're in. If you don't,
the image tags don't work; the documentation isn't self-contained, but depends on having the source tree as well.

There are workarounds for including non-generated files with the generated ones, like the one described in
http://rubyforge.org/tracker/index.php?func=detail&aid=3189&group_id=627&atid=2475

I think a better solution would be for rdoc to copy locally linked images into the output directory and rewrite the
img tag's path accordingly. The files could be placed into a single directory called "images", and linked
from there.

This behavior would probably break some peoples' existing documentation setup, so it should be controlled by a flag
like "--copy-local-images".