optimization of how often fluxbox checks for the system time to display it in the clocktool
optimization of how often fluxbox checks for the system time to display it in the clocktool

the idea (as a first patch) for this change was provided by
Thomas Habets (thomas at habets pp se). instead of having a
fixed interval each second, we now calculate the next point in
time based upon the format string used by the clocktool to render
the time. as long as no seconds are shown fluxbox now wakes up
once every minute.

olivergondza/fluxbox,luebking/fluxbox,lukoko/fluxbox,luebking/fluxbox,Arkq/fluxbox,luebking/fluxbox,Arkq/fluxbox,olivergondza/fluxbox,olivergondza/fluxbox,luebking/fluxbox,luebking/fluxbox,lukoko/fluxbox,lukoko/fluxbox,naimdjon/fluxbox,Arkq/fluxbox,naimdjon/fluxbox,naimdjon/fluxbox,Arkq/fluxbox,Arkq/fluxbox,lukoko/fluxbox,olivergondza/fluxbox,olivergondza/fluxbox,naimdjon/fluxbox,lukoko/fluxbox,naimdjon/fluxbox