Pull RCU updates from Paul E. McKenney:
  * Remove restrictions on no-CBs CPUs, make RCU_FAST_NO_HZ
    take advantage of numbered callbacks, do additional callback
    accelerations based on numbered callbacks.  Posted to LKML
    at https://lkml.org/lkml/2013/3/18/960.
  * RCU documentation updates.  Posted to LKML at
    https://lkml.org/lkml/2013/3/18/570.
  * Miscellaneous fixes.  Posted to LKML at
    https://lkml.org/lkml/2013/3/18/594.
Signed-off-by: Ingo Molnar <mingo@kernel.org>