[PATCH] sched: update Documentation/sched-stats.txt

While learning about schedstats I found that the documentation in the tree
is old.  I updated it and found some interesting stuff like schedstats
version 14 is the same as version and version 13 never saw a kernel
release!  Also there are 6 fields in the current schedstats that are not
used anymore.  Nick had made them irrelevant in commit
476d139c but never removed them.

Thanks to Rick's perl script who I borrowed some of the updated descriptions
from.
Signed-off-by: Joachim Deguara <joachim.deguara@amd.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: Rick Lindsley <ricklind@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>