New init.d script interpreter /lib/init/init-d-script.

* Transform init.d/skeleton into an init.d script interpreter
  /lib/init/init-d-script in sysvinit-utils that can be reused by other
  init.d scripts to avoid duplicate code (Closes: #464854).  See
  init-d-script(5) for how to use it.
* Rewrite service to detect status support by running scripts with
  'status' as the argument, and look for usage description.