I've attached two patches:

1. Patch 0001 is the code patch from before, with the warnings from make
addressed.

2. Patch 0002 is the documentation patch, which adds to ORG-NEWS and the
manual.  There are two new sections -- one is in the appendix under
"Hacking", and shows how to add a preview function for a link type
(along with a code example).

>> Should I rename the node "(org) Images" to something else, like "(org)
>> Images and supported links"?
>
>> Should I create a new node instead under (info "(org) Markup for Rich
>> Contents"), titled "Links"?
>
> I feel that it may be too obscure. I'd prefer an emphasis on images in
> the node titles - that's what new users can recognize better.
>
> Maybe rename "Images" to "Images and previews" and then put two
> subsections inside - one for images (the existing one) and one for more
> general link previews.

The other is the node that was previously "Images", and does what you
suggest here.

Karthik