Handle pdfs where freed objects have not been properly marked as free in xref.
Handle pdfs where freed objects have not been properly marked as free in xref.

darcs-hash:20090823221019-86a4e-0e9329f8f2a88c79bb87bb12356b02af9edd4cd2.gz

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