sched, tracing: Show PREEMPT_ACTIVE state in trace_sched_switch

sched, tracing: Show PREEMPT_ACTIVE state in trace_sched_switch

We had need to see the difference between scheduling a runnable task and
a runnable task being involuntarily preempted.

No app should rely on the old string output (the binary
trace event record format is not changed).

Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Steven Rostedt <[email protected]>
Link: http://lkml.kernel.org/r/1316164603.10174.11.camel@twins
Signed-off-by: Ingo Molnar <[email protected]>