Documentation updates for 3.20

Hello!

This series contains a few documentation updates:

1. Updates the sysfs path for rcu_cpu_stall_timeout, courtesy of
Xie XiuQi.

2. Records limitations of bitfields and small variables, noting
among other things that safe concurrent update to adjacent non-bitfield scalar variables is required by the C11 standard.

3. Fix typo in memory-barriers.txt, courtesy of Davidlohr Bueso.

Thanx, Paul

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 b/Documentation/RCU/stallwarn.txt   |    2 -
 b/Documentation/memory-barriers.txt |   46 +++++++++++++++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 2 deletions(-)