Last night I compiled 21.2 from the latest CVS sources to check out
Daniel Pittman's new athena configuration stuff.  Here's what I found
along the way.
1. Even though I had been successfully building with Xaw3d, I hadn't
   installed the 3d headers.  If I understand the emails which had
   been passing back and forth, this was a good recipe for a crash.
   The new configuration code warned me about this and defaulted to
   plain old athena.  Good job, Daniel.
2. Next I installed the neXtaw library (into the default location
   generated by xmkmf) and the header files ended up in
   /usr/X11R6/include/neXtaw.  (This is a Mandrake 6.1 system, BTW).
   The new configuration code could not find the headers in this spot,
   so I added a symlink from /usr/X11R6/include/X11/neXtaw to
   /usr/X11R6/include/neXtaw; this made the neXtaw configuration work
   fine.  Daniel, I don't know if you want to support
   /usr/X11R6/include/neXtaw, it seems like a good idea to me, but you
   have a much better idea than I do.
3. (Off topic) OK, now I have this XEmacs with this spiffier scrollbar
   - is it possible to get this to scroll by more than one line?  This
   seems like the most feeble (and slowest) scrollbar I've ever used;
   why would I want it?
Anyway, that's what I found.  Nice work, Daniel.
  - vin