Move /sbin/brltty to /bin/brltty

  * rules: Let brltty get installed into /bin, so it can be run e.g. in X for
    accessing terminals.
  * brltty.links: Add compatibility symlink in /sbin/brltty.
  * brltty-udeb.dirs, brltty-udeb.sh, brltty.dirs, brltty.init,
    brltty.install, brltty.service, xbrlapi.install, 20-sbin.patch: Update
    accordingly.