For the time being, we'll just package the upstream-generated
manual.pdf, since we can't build the PDF reproducibly ourselves.
The reason we can't is most probably due to the fact that the
LaTeX document embeds other PDF documents and PNG images.
Although we are able to reproduce the PDF's creation and mod
dates, as well as its PDF IDs, the stream elements representing
the embedded images are always what seem to differ each time we
try to generate the PDF.
Use absolute paths to compensate for the fact that we don't install
duplicates in /usr/share/doc/dvdisaster-doc or build with source
path embedded anymore.
Don't patch the documentation directly, to avoid one extra patch
in divergence from upstream.
Use the BUILDROOT variable instead of setting BINDIR etc during
installation.
