Drop multiarch-find-lib, let dante-client put just the names of
the preloaded libraries into LD_PRELOAD, let the runtime loader worry
about their ABI.

To achieve that, put libdsocksd directly into $libdir so that the loader
can actually find it; hence, build libdsocksd as a fully-versioned library,
SONAME and its own binary package and symbols file and all.

Make dante-client an architecture-independent package that just depends on
the arch-specific libdsocksd0 library.

Update the changelog.