Turn hrtimers into a range capable timer

This series is a follow-on the the nanosecond select/poll series.

The goal of this series is to introduce the capability into hrtimers to
deal with a "range" rather than a specific point in time.
(Several people discussed this recently, but we've been toying with the
concept for a while)

In addition, in the last patch of the series, the patches make select()
and poll() use these range timers with a standard "slack" that comes
from
1) a per process task_struct value
2) a "the longer the sleep the more the slack" function that Linus wrote