This label is visible when the currently focused client is in floating mode and
detached from the layout. It uses the focused_state_change_event as well as the
focused_client_change_event to check if the focused client is floating and
updates m_is_floating accordingly which will enable/disbale the floating label
in the final output.
update_floating_label is called when the floating state of the client is not
known. The function queries dwm for the properties of the focused client and
sets m_is_floating accordingly.
This fixes issue #2.
02bd2e060d