[$] Better CPU selection for timer expiration

On the surface, the kernel's internal timer mechanism would not appear tohave changed much in a long time; the core API looks quite similar to theone present in the 1.0 release. Underneath the API, naturally, quite a bitof complexity has been added over the years. The implementation of thisAPI looks to become even more complex - but faster - if and when this patch set from Anna-Maria Behnsen finds its way into the mainline.