Use a slower but correct division in image bit depth scaling/clamping.
Use a slower but correct division in image bit depth scaling/clamping.

darcs-hash:20090408111643-f546f-f6260cbb51242492c945e915fa35586d9cfeef44.gz

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