- timestamp sources on update so we don't over update them due to multiple visualizations hammering on it. improves our tick situation even more.
svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=712188
this is needed by clocks, as the obvious example, since "once a minute" isn't enough: it needs to be once a minute *on* the minute
svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=711737