Add Documentation/RCU/00-Index

Add Documentation/RCU/00-INDEX

Signed-off-by: Rob Landley <rob@landley.net>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>