This fixes the problem of the missing man pages in libam7xxx0.1-bin when
building only the binary packages.
Building the man pages depends on asciidoc, and the man pages need to be
built along with libam7xxx0.1-bin which is a binary package; however
dependencies in Build-Depends-Indep are not brought in when doing
a binary only build.
xmlto is needed as well because the a2x program from asciidoc needs it.