Remove a cast now that md5 buffers are const.
Remove a cast now that md5 buffers are const.

darcs-hash:20080930205903-cac71-803dc68a9710dbe59d07482d7493fe659c445ca8.gz

nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf