The fix from upstream did not apply cleanly due to many context changes.
This was adapted by cloning mupdf 1.9a from git and fixing conflicts
after applying our patches and cherry-picking upstream commit 1e03c06.
This is a follow-up to 47a04fca99.
* gnu/packages/patches/mupdf-CVE-2016-8674.patch: Adapt to 1.9a.