[$] Deadline servers as a realtime throttling replacement

The CPU scheduler's one job at any given time is to run the task that hasthe strongest claim to the CPU. There are many factors that complicatethat job, not the least of which is that the "strongest claim" is sometimesa bit of a fuzzy concept. Realtime throttling, a mechanism designed tokeep a runaway realtime task from monopolizing the CPU, is one case wheredevelopers have concluded that the task with, ostensibly, the highestpriority should not actually be the one that runs. But realtime throttlinghas rarely pleased anybody; the deadline-serverinfrastructure patches posted by Daniel Bristot de Oliveira are thelatest attempt to find a better solution.