Russel Coker thinks you're too sloppy with const among other things. See http://bugs.debian.org/524133. Here is a patch. Naturally, you have to enable warnings to see them. :-)
Russel Coker pointed out (see http://bugs.debian.org/532740) that libdkim uses strtok(), which is not reentrant, making libdkim unsuitable in multithreaded applications. His patch is attached.
