We have VTY support for it enabled in osmo-pcu since a while ago. Let's
mark it as depcreated now so that we can drop this cmdline arg in the
future.
Change-Id: Ic39c94984cb311aac0464d69f564af6d5447bd0f
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.