sched: re-do "sched: fix fair sleepers"

re-apply:

| commit e22ecef1d2658ba54ed7d3fdb5d60829fb434c23
| Author: Ingo Molnar <mingo@elte.hu>
| Date:   Fri Mar 14 22:16:08 2008 +0100
|
|     sched: fix fair sleepers
|
|     Fair sleepers need to scale their latency target down by runqueue
|     weight. Otherwise busy systems will gain ever larger sleep bonus.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --cc kernel/sched_fair.c
Simple merge