Make courier-autlib ports run the sysconftool on installation, as
suggested by upstream, like courier-imap port does.

The sample files are renamed to ".dist" because that is the name
the tool expects.

Also added a note to UPDATING to warn users about the sysconftool
expecting the comments not to be removed.

While here convert to localbase.

Suggested by: Doug McIntyre <merlyn at iphouse.net>