This rewrite is based on a TODO comment for the *stack_refresh*
function of *awesome*:
It might be worth stopping to restack everyone and only stack `c'
relatively to the first matching in the list.
And on the concept of relative stacking (via XDG_CONFIG_WINDOW_SIBLING).
Additionally the `adaptative_raise` setting was removed because it
became obsolete when the choice was made of not raising windows when
focusing via `focus_follows_pointer`.
Windows of type *desktop* are now supported (but not managed).
The new message syntax:
- Provides 10 commands instead of 60.
- Allows multiple actions to be applied in one call.
The client now returns an non zero exit code when a message fails.
The `is_adjacent` function now handles vacant nodes.
