At various places we sort our D-Bus paths. For example,
server sorts them before exporting them on D-Bus.
Server knows well, that a lot of these paths are build
by attaching an incrementing number as last component.
It looks nicer to sort by this number, instead of strictly
lexical with strcmp().
Note that this handles the cases correctly where paths have
different prefixes, or where they don't end with a number.
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