This is a bit awkward, as the 'revnumber' asciidoc variable so far
doesn't seem to end up in the docbook-xml. We now put it into
'releaseinfo' which gets then put into \DBKreleeaseinfo by dblatex.
makefile watermark fixup
The manuals existed in different form for several years in an internal
sysmocom repository. However, since they had just recently been
converted from docboox-xml to asciidoc and all files have been
re-shuffled for enabling the public release, there's not much point in
keeping the history with git-filter-branch.