> > A callback that would signal: "Hey you,
> > it's time to update your timer!"

> I'll just save that task for an upcoming release unless
> someone else is interested in implementing it sooner.

Well, here is a shot at the easy part.

This adds the prototype and constants to multi.h, the two
extra fields to the Curl_multi struct, and the extra switch
cases to curl_multi_setopt. (I assume the callback doesn't
need to be propagated down to the easy-handle level.)

I also took a stab at writing an internal "update_timer" function,
but someone with a deeper understanding of the inner workings of
the timer tree needs to decide all the different places where the
call needs to be plugged in. I picture that it only needs to get
called whenever the timetree gets modified, but that's probably
way too simple.

 - Jeff