r20394: This is a *VERY* early start of my work on notify.

r20394: This is a *VERY* early start of my work on notify.

Checking in because Jeremy was bugging me. Potentially this becomes quite
intrusive, I'm not sure if I should open a temporary branch for this.

Jeremy, Jerry, do you think 3_0 is the right place for this?

Volker
(This used to be commit bcf5c751cbe203c00814642e26440cf88f300bce)