add dirac.c as a source file to the oggz tools, rather than a lib.

The previous would try to compile at link time, and would not include the
right -I flags, and this will fail when including config.h in dirac.c
Patch by ogg.k.ogg.k:
http://lists.xiph.org/pipermail/ogg-dev/2008-December/001319.html

git-svn-id: http://svn.annodex.net/liboggz/trunk@3834 8158c8cd-e7e1-0310-9fa4-c5954c97daef