olsrd: report the packaged version in the binary

olsrd: report the packaged version in the binary

olsrd builds its version banner from the VERS make variable, which
defaults to the upstream development version "pre-0.9.9", so
`olsrd -v` never mentioned the version the package was built from.
The source tarball carries no git metadata either, so the git hash
in that string is always zero:

    olsr.org - pre-0.9.9-git_0000000-hash_5fd8976...

Pass PKG_VERSION as VERS, the same way alfred and batctl already
pass REVISION, so the banner identifies the packaged revision. This
also lets test-version.sh check the real version instead of merely
confirming that the binary starts.

Signed-off-by: Josef Schlehofer <redacted>
Co-authored-by: Claude Fable 5 <redacted>